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  • Articles  (93)
  • Yeast  (93)
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  • 1995  (35)
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  • Articles  (93)
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  • 1995-1999  (35)
  • 1985-1989  (38)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 111 (1980), S. 355-363 
    ISSN: 1434-4475
    Keywords: Cerulenin ; Fatty acid donor ; Inositol deficiency ; Phospholipid biosynthesis ; Triacylglycerols ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Der Umsatz der Lipide vonSaccharomyces carlsbergensis ATCC 9080 wurde nach Vormarkierung mit3H-Ölsäure und14C-Palmitinsäure untersucht. Inositversorgte Zellen zeigen eine Verschiebung der Fettsäuren von den Triacylglycerinen in die Phospholipide, im besonderen in Phosphatidylcholin und Phosphatidylinosit. Eine verstärkte Übertragung der Fettsäuren von Triacylglycerinen auf Phospholipide konnte festgestellt werden, wenn vormarkierte Zellen auf ein Nährmedium, welches Cerulenin enthielt, übertragen wurde. Cerulenin inhibiert die Fettsäuresynthese und ruft in wachsenden Zellen Fettsäuremangel hervor. Inositdefiziente Hefezellen, welche einen erhöhten Triacylglycerinspiegel aufweisen, verwenden diese Triacylglycerine unter Fettsäuremangelbedingungen ebenfalls für die Synthese von Phospholipiden, besonders von Phosphatidylcholin, Phosphatidyläthanolamin und Phosphatidylserin. Da aus früheren Arbeiten bekannt ist, daß inSaccharomyces carlsbergensis praktisch keine β-Oxidation existiert, können die Triacylglyerine in diesem Hefestamm als Speicher für Fettsäuren angesehen werden, welche zur Synthese von Phospholipiden dienen.
    Notes: Abstract The turnover of lipids was studied in the yeast,Saccharomyces carlsbergensis ATCC 9080, after prelabeling of the cells with [3H] oleic acid and [14C] palmitic acid. In inositol supplemented cells, a redistribution of fatty acids from triacylglycerols to phospholipids (mainly phosphatidylcholine and phosphatidylinositol) could be demonstrated. An increased transfer of fatty acids from triacylglycerols to phospholipids was observed when prelabeled cells were transferred to a growth medium containing cerulenin, which inhibits fatty acid synthesis and thus induces fatty acid deficiency in the growing cells. Inositol deficient cells contain increased levels of triacylglycerols, which are equally well utilized for phospholipid (mainly phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine) synthesis under conditions of fatty acid deficiency. The present results together with the previous finding that β-oxidation is practically absent inSaccharomyces carlsbergensis suggest that in this yeast triacylglycerols function as storage of fatty acids which can be mobilized for phospholipid biosynthesis.
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  • 2
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Intragenic recombination ; Mutant polypeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recombinational analysis of oxil mutants was performed using a and a mutant strains with the same mitochondrial and nuclear backgrounds, derived from strain 777-3A. In spite of minor inconsistencies the overall map of oxi1 mutations can be constructed on the basis of wild-type recombinant frequencies in the two-point oxi1 − − x oxi1 − crosses. The frequencies of wild-type recombinants varied in a wide range from 0.003% to 16%, reaching the maximal values expected for unlinked mitochondria) markers. No distinct clusters of mutants were observed. The analysis of translation products of oxil mutants showed that all but one of the oxil mutants studied are connected with the conspicuous changes of the polypeptide band corresponding to subunit 11 of cytochrome c oxidase in electrophoresis on polyacrylamide gels. The exceptional G565 mutant showed no conspicuous change in subunit II, but lacked subunit I of cytochrome c oxidase. Various oxi1 mutants seemed to carry premature chain termination mutations. Most of them show a correlation between the length of the putative fragment of subunit II synthesized and the position on the genetic map. The direction of translation is from the V2 to the V60 mutation. The V2 mutation is proximal to cap and V60 proximal to the par locus.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 2 (1980), S. 61-67 
    ISSN: 1432-0983
    Keywords: Axenomycin ; Ribosome genetics ; Yeast ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Axenomycin inhibits protein synthesis in vivo and in vitro in Saccharomyces cerevisiae. The antibiotic acts by binding to ribosomes, most probably to the large ribosomal subunit. Mutant strains resistant to axenomycin appear to contain ribosomes that are not inhibited by the antibiotic. The responsible gene has been mapped on the VII chromosome between the centromere and the leu1 gene.
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  • 4
    ISSN: 1432-0983
    Keywords: Tetrahymena ; Replication ; Segregation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have previously demonstrated that a 657 bp TaqI-XbaI and a 427 by XbaI-XbaI fragment from the 5′ non-transcribed spacer of the extrachromosomal ribosomal DNA of Tetrahymena thermophila function as autonomously replicating sequences (ARS) in Saccharomyces cerevisiae. These fragments are adjacent to each other in a region that encompasses the in vivo origin of bidirectional replication of rDNA. The presence of a yeast centromere (CEN) fragment does not confer mitotic stability on these plasmids. A sensitive yeast colony colour assay (Hieter et al. 1985a) has been used to evaluate the cis-acting effect of each ARS segment on the pattern of inheritance of a plasmid containing CEN5:URA3:SUP4. Colonies of transformed cells obtained both in the presence and absence of selection were red with no detectable white or pink sectors. The lack of sectoring indicates that both plasmids are lost at an extremely high rate, likely due to 1:0 segregation events. We conclude that while these ARS elements confer a high frequency transformation phenotype, they lack a function which is required in cis for the maintenance of mitotic stability in the presence of a centromere. This missing cis-acting function may result in the inability of the plasmids to be brought under the control of cell-cycle regulated replication.
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  • 5
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial ; Mutants ; RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This is a description of a new class of temperature sensitive pet mutants in Saccharomyces cereviase that lose all or part of their mitochondrial RNA at the restrictive temperature. These mutants fall into 8 different complementation groups, mna1 to mna8, and 2 different classes based on their phenotype. Class I mutations, mna1-1 through mna5-1, cause complete or partial loss of mitochondrial RNA at the restrictive temperature. The mutation, mna1-1, is especially interesting since it causes a loss of both mitochondrial DNA and RNA when the mutant is grown on a fermentable carbon source at the restrictive temperature. However, when this mutant is grown at the permissive temperature on a non-fermentable carbon source then shifted to the restrictive temperature, only the mitochondrial RNA is lost. This indicates that the primary cause for the pet phenotype is due to the loss of mitochondrial RNA and not DNA. Class II mutations, mna6-1 through man8-1, cause complete loss of the 14S rRNA after growth at the restrictive temperature in a fermentable carbon source. This loss appears to be specific for the 14S rRNA, since all other transcripts probed by Northern analysis are normal.
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  • 6
    ISSN: 1432-0983
    Keywords: Yeast ; Disomy for chromosome IV ; Mitochondrial rho − mutability ; Mitotic chromosome loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The disomy for chromosome IV in the strains studied led to: i) a reduction in the red pigmentation of ade1 mutant colonies; ii) a decrease of the spontaneous rho − mutant frequency, and iii) an impairment of sporulation in hybrids descended from disomic parents. The nuclear srm1 mutation decreasing the spontaneous rho − mutability promoted the spontaneous extra chromosome loss in the disomes for chromosome IV. This result suggests a close connexion between the spontaneous rho − mutability and mitotic chromosome stability.
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  • 7
    ISSN: 1432-0983
    Keywords: Y. lipolytica ; LEU2 ; Yeast ; Leucine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A 2810 by DNA fragment containing the beta-isopropylmalate dehydrogenase gene of the dimorphic yeast Yarrowia lipolytica has been sequenced. The sequence contains an open reading frame of 405 codons, predicting a protein of 43,366 molecular weight. Protein sequence homology with the polypeptide encoded by the LEU2 gene of Saccharomyces cerevisiae is 64%, whereas DNA sequence homology is 61%. The 5′- and 3′-flanking regions of the Y. lipolytica LEU2 gene share only some general structural features common to genes of S. cereviside such as the presence and location of TATA boxes, CAAT boxes, CACACA repeats, the lack of G residues in the 5′-untranslated region and 3′-transcription terminators. Transcription of a 1.4 kb mRNA begins at a small cluster of sites approximately 40 base pairs before the initial ATG.
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  • 8
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    Current genetics 11 (1987), S. 411-413 
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial rho − mutability ; Genetic analysis ; Modifying genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The phenotypic trait “starry colony” in Saccharomyces is associated with a high spontaneous rho − petite mutability. Genetic analysis of this trait has shown the high rho − mutability to be caused by several modifying genes present together in the strains studied. Every single modifying gene produces only a relatively small enhancement of the rho − mutability.
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  • 9
    ISSN: 1432-0983
    Keywords: Yeast ; Mutagenesis ; Base analogues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cells of the yeast, Saccharomyces cerevisiae, which are auxotrophic for thymidylate (tmp1) can also incorporate analogues of thymidylate. When the base analogue, 5-bromodeoxyuridylate, is incorporated into tmp1 yeast cells it is lethal and mutagenic. Both lethality and mutation induction can be drastically altered by perturbation of the pyrimidine nucleotide pools. Analysis of mutation induction, bromodeoxyuridylate incorporation into DNA, and cell viability under various conditions revealed: (1) lethality and mutagenesis can be uncoupled, (2) thymidylate enhances mutagenesis and deoxycytidylate suppresses it, (3) mutation induction is not correlated with the magnitude of bromodeoxyuridylate incorporation into DNA. Therefore, in yeast, the pyrimidine nucleotide pools have a powerful effect on bromodeoxyuridylate mutagenesis. Both bromodeoxyuridylate and iododeoxyuridylate are extensively incorporated into the DNA of tmp1 yeast cells; however, iododeoxyuridylate is non-mutagenic. Replication proceeds at the same rate in the presence of the natural substrate or either analogue. When cells are supplied with thymidylate and bromodeoxyuridylate together, there is no discrimination against bromodeoxyuridylate as a DNA precursor. However, in the presence of thymidylate and iododeoxyuridylate, there is a 3 to 1 discrimination against iododeoxyuridylate as compared to thymidylate.
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  • 10
    ISSN: 1432-0983
    Keywords: Kluyveromyces lactis ; Yeast ; Extrachromosomal inheritance ; Antimycin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Antimycin-resistant (AR) mutants of the yeast Kluyveromyces lactis, obtained either spontaneously or after manganese treatment, were isolated and genetically characterized. Most of the mutants obtained after manganese mutagenesis and two spontaneous mutants, tolerated high antimycin concentrations (more than 10 /gmg/ml) and were extrachromosomal. One mutant which grew only in low antimycin (1 /gmg/ml) showed a Mendelian type of inheritance. The extrachromosomal mutants could be assigned to at least two genetic loci (A I R and A II R ). Mutants representative of these two groups showed increased resistance to the antibiotic when the respiration of whole cells or mitochondria was studied. Extrachromosomal mutants of Saccharomyces cerevisiae resistant to antimycin were also induced with manganese, isolated and characterized. Comparative studies of the antimycin-resistant mutants of K. lactis and S. cerevisiae permitted the following observations: a) K. lactis is more resistant to antimycin, funiculosin, mucidin and diuron than S. cerevisiae, as are the AR mutants; b) K. lactis shows correlated sensitivity to funiculosin differing in this aspect from S. cerevisiae; c) the antimycin-resistant mutants of K. lactis belonging to group 11 (A II R ) were also resistant to diuron, tolerating concentrations of more than 200 /gmg/ml; d) all extrachromosomal antimycin-resistant-mutants of S. cerevisiae and some of the AR mutants of K. lactis were more sensitive to mucidin than the wild type.
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  • 11
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Translation ; Informational Suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phenotypic suppression by the antibiotic, paromomycin, of the mitochondrial oxi1 −-V25 mutation, a mutation which arrests by premature ochre codon the synthesis of the cox 11 subunit, was studied in isolated yeast mitochondria competent in translation. This antibiotic is known to suppress the mutation in vivo (Dujardin et al. 1984) and allowed in vitro, at concentrations of 20–1100 Mg per ml. the synthesis of the cox II subunit. This strongly suggests that phenotypic suppression of mit − mutations is due to the direct action of paromomycin on mitochondrial ribosomes. The effect of paromomycin bears a resemblance to the function of the omnipotent nuclear suppressor mutation R705. The nuclear suppression was expressed in isolated mitochondria; suppressor mutation influenced the structure of the mitoribosome. Therefore, it appears that mitoribosomes are indeed the common target in the phenotypical and genetic nuclear suppression of the oxi1-V25 mutation.
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  • 12
    ISSN: 1432-0983
    Keywords: Yeast ; ARS-like activity ; Petite genome replication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seven MboI fragments spanning the mitochondrial apocytochrome b gene in Saccharomyces cerevisiae strain D273-10B were cloned in the BamHI site of the integrative yeast vector YIp5 and the capacity for autonomous replication was subsequently assayed in yeast. The positive correlation found between the ars-like activity in four fragments and the presence of regions common to multiple ethidium bromide-induced petite (rho−) genomes suggests that the mitochondrial sequences possibly active as origins of replication in low-complexity neutral or weakly suppressive rho− mutants could be functionally related to the yeast nuclear replicator 11 nucleotide motif defined by Broach et al. (1983).
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  • 13
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    Current genetics 2 (1980), S. 207-210 
    ISSN: 1432-0983
    Keywords: Yeast ; Plasmid ; Repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have developed a system for assaying pyrimidine dimers in the 2 ⇐m DNA plasmid of Saccharomyces cerevisiae, using Micrococcus luteus UV endonuclease to nick dimer-containing plasmid molecules and measuring percentages of nicked and covalently closed circles on agarose gels. UV-irradiation induced dimers in plasmid DNA, in vivo, at the same rate as in chromosomal DNA. After a dose of 20 Joules·m−2, approximately 86% of plasmid molecules had. at least one dimer. After 3 h incubation under normal growth conditions only 4% still retained dimers in a wild-type strain. In a rad1 (excision-defective) mutant 81% of plasmid molecules still had dimers after 3 h, suggesting that excision repair operates to remove dimers from plasmid DNA in wild-type yeast. Dimers can be removed from 2 ,um DNA in a rad1 mutant by photoreactivation.
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  • 14
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    Current genetics 2 (1980), S. 211-214 
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein dimorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two-dimensional gel electrophoresis was used in a comparative study of ribosomal proteins from various strains of Saccharomyces cerevisiae. The results demonstrated a case of dimorphism of L8 protein of 60S ribosomal subunit. Of eight strains examined, two strains were one type and six were the other type. The former, which was tentatively designated as altered (A) type, was more acidic than the latter, common (C) type, as shown by mobility difference in pH gradient gel. Heterozygous (A/C) diploid cells contained both types of L8 protein and gave rise to tetrads of 2:2 segregation for A and C types, indicating that the difference of mobility was reflection of the allelic difference of the gene coding for L8 protein.
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  • 15
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    Current genetics 1 (1980), S. 177-183 
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein alteration ; Cycloheximide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A spontaneous high-level cycloheximide-resistant mutant of the yeast Saccharomyces cerevisiae (strain cy32) is found to have an altered protein of the large subunit (60S) of cytoplasmic ribosomes, namely protein L29. The resistance character segregates together with this biochemical defect and is semidominant in heterozygous diploids. Judged from in vitro susceptibility to inhibition by cycloheximide there are at least 50% resistant ribosomes present in such diploid strains. From these results it is concluded that cycloheximide resistance of mutant cy32 is caused by mutation of a single gene and that it is the structural gene for L29 which is affected. Preliminary genetic mapping data are also reported. They indicate a location of cyhx-32 marker on chromosome 7 near met13.
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  • 16
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial ; Frameshift-Suppression ; 15S rRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The first case of a +1 “extrageneic” frameshift suppressor (MF1), mapping in the yeast mitochondrial 15S rRNA gene is reported. The suppressor was identified by genetic analyses in a leaky mitochondrial oxi1 frameshift mutant and the respective wild-type strain 777-3A of the yeast S. cerevisiae. This is in accordance with the finding that all mitochondrial frameshift mutants isolated from this strain tend to be leaky to a variable degree. MF1 does not suppress known nonsense mutations created by a direct basepair exchange in strain 777-3A. These mutants exhibit a non-leaky phenotype (Weiss-Brummer et al. 1984).
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  • 17
    ISSN: 1432-0983
    Keywords: Yeast ; Nuclear ploidy ; Critical size ; Cell proliferation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary For a polyploid series of Saccharomyces cerevisiae strains ranging from haploid to tetraploid we found that the critical cell size required to initiate a new cell division process was directly and linearly proportional to ploidy, but was not influenced by the information at the MAT locus which determines cell type. Therefore, over at least a four-fold range in ploidy the cell cycle machinery which is responsive to growth is modulated by nuclear DNA content.
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  • 18
    ISSN: 1432-0983
    Keywords: Yeast ; Ploidy ; Isogenic ; Ethanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Effects on ethanol production by increases in gene dosage independent of heterosis in yeast are compared for an isogenic ploidy series ranging from haploid to tetraploid. The per-cell rate of ethanol accumulation in parallel batch cultures increases with cell ploidy, and is attributable to intrinsic, ploidy-associated increases in cell mass-adjusted ethanol production rates. This increase in per-cell ethanol accumulation in the tetraploid strain is as high as 6.9 times the level of accumulation in the haploid. That is, the efficiency of ethanol production per unit cell mass is greater in cells of higher ploidy.
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  • 19
    ISSN: 1432-0983
    Keywords: Heat shock ; Thermotolerance ; Ploidy ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The resistance of Saccharomyces cerevisiae to inactivation by DNA damaging agents has long been known to be affected by cell ploidy. Resistance is greater for diploid than for haploid cells, but exhibits decreases for further increases in ploidy beyond diploid. In this study S. cerevisiae cells whose genomes differ only in their ploidy were employed to investigate how ploidy directly influences resistance to thermal killing. In virtually all species resistance to thermal killing is a cellular property that is elevated by heat shock and other agents that induce the heat shock response. We therefore investigated how ploidy affected the thermal killing of S. cerevisiae cells both before and after elevation of thermotolerance by means of a 40 min 25 °C to 38 °C heat shock. Without such induction of thermotolerance there was negligible effect of ploidy on thermal killing. In contrast in the heat shocked cultures there was an appreciable decrease in thermotolerance as ploidy increased. This difference indicates that the lethal thermal damage in the thermotolerance induced cultures is not totally equivalent to that in cells not given a prior heat shock, and that gene expression changes after heat shock result in a ploidy effect on heat tolerance which is absent from cells in which the heat shock response has not been induced.
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  • 20
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    Current genetics 12 (1987), S. 569-576 
    ISSN: 1432-0983
    Keywords: Yeast ; Disomy ; Meiotic dyads
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Among meiotic asci produced by triploid (3N) Saccharomyces cerevisiae are cases in which exactly two of the four ascospores proliferate into colonies. Given the unique asymmetry problems inherent in distributing three chromosome homologues in meiosis, these ascospore dyads are of special interest. We have tested 40 of these dyads (80 ascospores) for their chromosome content by ascertaining whether they have inherited one or two copies of each of the sixteen yeast chromosomes from the parental triploid. Overall, then, ascospores in these dyads can be either haploid (N) or disomic (N + 1) for each chromosome. The principal results of this analysis include: (1) Coincident disomy (inheritence of two copies of a given chromosome in both members of an ascospore dyad) was detected for 15 of the 16 yeast chromosomes, and at least once in every dyad. (2) Coincident disomy increased as a function of the mean number of disomic chromosomes per spore in each dyad, but this increase differed functionally from that expected if coincident disomy in the two ascospores were a simple, meiotically independent, concomitant of multiple disomy. We conclude from these results that: (1) The ascospore dyads, as the two proliferating spores of single meioses from the triploid, represent meiotic sisters. That is, they stem from the same half of the first meiotic division. (2) Multiply-disomic meiotic segregants of yeast triploids proliferate at the expense of their multiple disomy, as cells in spore colonies experience repeated and independent disomic chromosome losses (N + 1 → N). (3) Aneuploid generation in triploid meiosis is chromosomally unbiased and is the consequence of the independent two-by-one segregation at MI of every homologous triad.
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  • 21
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    Current genetics 2 (1980), S. 175-180 
    ISSN: 1432-0983
    Keywords: Yeast ; Hydroxyurea ; DNA synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Newly synthesised DNA molecules the same size as replicons (7 million-60 million daltons) accumulate in yeast cells treated with hydroxyurea. During prolonged incubation in low concentrations of the drug, there is a large accumulation of these molecules without any corresponding increase in their molecular weight. On release from the inhibtion the molecules are converted to large molecular weight DNA. These observations are consistent with an inhibition by hydroxyurea of the joining of completed replicons. In addition, newly synthesised DNA molecules the size of yeast Okazaki fragments also accumulate in cells treated with hydroxyurea.
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  • 22
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    Current genetics 2 (1980), S. 193-200 
    ISSN: 1432-0983
    Keywords: Recombination ; Plasmids ; Transformation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary [2 μm+ and [2μm°] yeast were transformed to stable leucine prototrophy with the hybrid yeast — E. coli plasmid, pJDB219. This plasmid contains the entire sequence of the endogenous 2 μm yeast DNA plasmid in addition to the yeast nuclear LEU2 + gene and the Co1E1 derivative, pMB9. In the [2 μm+] transformants, a new wholly yeast LEU2 + plasmid, pYX, was generated, probably by a recombination event between pJDB219 and 2 μm DNA. The plamid, pYX, in the absence of 2 μm DNA, was found to exist in equimolar amounts of two forms, A and B, which probably arise by intramolecular recombination across the inverted repeat sequences of the 2 μm DNA portion of the plasmid. pJDB219 was found to require the presence of 2 μm DNA to undergo this intramolecular recombination. The results suggest that 2, μm DNA and pYX code for a gene product required in this recombination event which pJDB219 cannot produce.
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  • 23
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    Journal of molecular evolution 24 (1987), S. 252-259 
    ISSN: 1432-1432
    Keywords: Histone genes ; Gene conversion ; Diploidization ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The core histone genes ofSaccharomyces cerevisiae are arranged as duplicate nonallelic sets of specifically paired genes. The identity of structural organization between the duplicated gene pairs would have its simplest evolutionary origin in the duplication of a complete locus in a single event. In such a case, the time since the duplication of one of the genes should be identical to that since duplication of the gene adjacent to it on the chromosome. A calculation of the evolutionary distances between the coding DNA sequences of the histone genes leads to a duplication paradox: The extents of sequence divergence in the silent component of third-base positions for adjacent pairs of genes are not identical. Estimates of the evolutionary distance between the two H3-H4 noncoding intergene DNA sequences are large; the divergence between the two separate sequences is indistinguishable from the divergence between either of the regions and a randomly generated permutation of itself. These results suggest that the duplication event may have occurred much earlier than previously estimated. The potential age of the duplication, and the attractive simplicity of the duplication of both the H3-H4 and the H2A-H2B gene pairs having taken place in a single event, leads to the hypothesis that modern haploidS. cerevisiae may have evolved by diploidization or fusion of two ancient fungi.
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  • 24
    ISSN: 1432-0983
    Keywords: Fungi ; S. crataegensis ; Yeast ; Plasmid ; Linear DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three DNA plasmids, designated pScrl-1, pScrl-2, and pScrl-3 have been found in a strain of the heterothallic yeast Saccharomycopsis crataegensis (NRRL Y-5902). pScrl-l, -2 and -3 are, respectively, 15, 7, and 5 kilobase pairs (kbp) in size. Based on the results of exonuclease digestions, all three plasmids appear to be linear molecules with blocked 5′ ends. All three plasmids also have a lower buoyant density than does nuclear DNA of S. crataegensis. The two lower molecular weight plasmids hybridize strongly with one another, but only weakly to the higher molecular weight plasmid. Two of four related S. crataegensis strains surveyed were found to contain two plasmids that are of the same size as the two larger plasmids of Y-5902. Evidence is presented indicating that the plasmids in strain Y-5902 reside in the cytosol since they were found not to be located within the major organelles (mitochondria and nuclei).
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  • 25
    ISSN: 1432-0983
    Keywords: Yeast ; Frameshift-Suppression ; Mitochondrial/Nuclear ; Interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Earlier genetic analyses have identified a mitochondrial +1 frameshift suppressor (MF1) in the 15S rRNA region of a leaky mitochondrial frameshift mutant and the respective wild-type strain 777-3A (Weiss-Brummer et al. 1987). Further genetic analyses revealed that for the observed spontaneous frameshift suppression in M5631 the mitochondrial factor (MF1) must act together with at least two dominant nuclear-encoded factors.
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  • 26
    ISSN: 1432-0983
    Keywords: HBsAg ; PEP4 ; Secretion ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The toxicity of HBsAg in the secretion pathway of pep4 strains can be progressively reduced in modified SD media containing lower concentrations of ammonium sulphate. A procedure, combining a reduction of ammonium sulphate concentration in SD media with the disruption of the PEP4 gene of the host strain, was developed to enrich transformants which are not inhibited by HBsAg expressed in the secretion pathway. Abnormal growth of these non-inhibited transformants is characterized by the enlargement of cell morphology, a transition to pseudohyphal-like growth in nitrogen-starved media, an increase in HBsAg particle production, and the enhancement of growth rate in liquid media. This suggests a new approach to overcoming the toxicity of heterologous protein in the yeast secretion pathway.
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  • 27
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    Current genetics 27 (1995), S. 509-516 
    ISSN: 1432-0983
    Keywords: Yeast ; Maltose fermentation ; MAL63 ; Saccharomyces cerevisiae
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    Notes: Abstract Mal63p is a transcriptional activator for maltose fermentation in Saccharomyces cerevisiae. We have purified it to homogeneity from a yeast strain in which the MAL63 gene is under the control of the GAL1–GAL10 promoter. Purification included fractionation of a whole-cell extract by ion-exchange chromatography, chromatography using both non-specific DNA-affinity (calf thymus), and sequence-specific DNA-affinity chromatography. Mal63p activity was assayed by its binding to a fragment of the MAL61–MAL62 promoter, using both filter-binding and electrophoretic-mobility shift assays. DNase-I footprinting identified a new binding site (site 3) between the two previously known sites (sites 1 and 2). Mal63p is a dimer, and methylation-protection experiments identify the recognition motif as: c/a GC N9 c/a GC/g.
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  • 28
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Translation ; mRNA 5′-leader
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    Notes: Abstract The 613-base 5′-untranslated leader (5′-UTL) of the Saccharomyces cerevisiae mitochondrial COX 3 mRNA contains the target of an mRNA-specific translational activator complex composed of at least three nuclearly encoded proteins. We have genetically mapped a collection of cox 3 point mutations, using a set of defined COX 3 deletions, and found one to be located in the region coding the 5′-UTL. The strain carrying this allele was specifically defective in translation of the COX 3 mRNA. Nucleotide-sequence analysis showed that the allele was in fact a double mutation comprised of a single-base insertion in the 5′-UTL (T inserted between bases-428 and-427 with respect to the start of translation) and a G to A substitution at+3 that changed the ATG initiation codon to ATA. Both mutations were required to block translation completely. The effects of the ATG to ATA mutation alone (cox 3-1) had previously been analyzed in this laboratory: it reduces, but does not eliminate, translation, causing a slow respiratory growth phenotype. The T insertion in the 5′-UTL had no detectable respiratory growth phenotype as a single mutation. However, the 5′-UTL insertion mutation enhanced the respiratory defective phenotype of missense mutations in pet 54, one of the COX 3-specific translational-activator genes. This phenotypic enhancement suggests that the-400 region of the 5′-UTL, where the mutation is located, is important for Pet54p-COX 3 mRNA interaction.
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  • 29
    ISSN: 1432-0983
    Keywords: Yeast ; Nucleo-mitochondrial interactions ; Introns ; RNA stability
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    Notes: Abstract The product of the nuclear gene SUV3 is implicated in a variety of post-transcriptional processes in yeast mitochondria. We have analysed the effect of SUV3 gene-disruption on the expression of intron-containing alleles of the mitochondrial cytb and coxl genes. We have constructed several strains with mitochondrial genomes containing different combinations of cytb and cox1 introns, and associated these genomes with the disruption of SUV3. The resulting strains were tested for their respiratory competence and spectral cytochrome content. All the strains containing only two or three introns showed normal expression of cytb and cox1, whereas the strains containing more introns were unable to express the appropriate gene. The analysis of mitochondrial RNAs by Northern hybridisation showed that the loss of respiratory competence in the strains containing more introns is due to the decrease of mRNA level with no over-accumulation of high-molecular-weight precursors. However, the transcription of the genes was not affected. These results led us to the notion that SUV3 is required for the stability of intron-containing cytb and cox1 transcripts in a cumulative way, not dependent on any particular intron.
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  • 30
    ISSN: 1432-0983
    Keywords: Yeast ; RAD58 ; Repair ; Recombination
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    Notes: Abstract The RAD58 (XRS4) gene of Saccharomyces cerevisiae has been previously identified as a DNA repair gene. In this communication, we show that RAD58 also encodes an essential meiotic function. The spore inviability of rad58 strains is not rescued by a spo13 mutation. The rad50 mutation suppresses spore inviability of a spo13 rad58 strain suggesting that RAD58 acts after RAD50 in meiotic recombination. The rad58-4 mutation does not prevent mitotic recombination events. Haploid rad58 cells fail to carry out G2-repair of gamma-induced lesions, whereas rad58/rad58 diploids are able to perform some diploid-specific repair of these lesions.
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  • 31
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    Current genetics 27 (1995), S. 330-338 
    ISSN: 1432-0983
    Keywords: Schwanniomyces occidentalis ; Yeast ; Hexokinase ; Glucokinase
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    Topics: Biology
    Notes: Abstract Hexose-phosphorylating enzymes from the starch-utilizing yeast Schwanniomyces occidentalis were purified and two isoenzymes separated. The substrate pattern characterized one of these as a hexokinase phosphorylating glucose and fructose and the other as a glucokinase unable to phosphorylate fructose. The purified Schw. occidentalis hexokinase had a KM value of 0.98 mM for glucose and 9.3 mM for fructose. The hexokinase gene was cloned by cross hybridization with a probe from the Saccharomyces cerevisiae HXK2 gene. Deletion of Schw. occidentalis hexokinase by gene replacement yielded a mutant unable to grow on fructose as sole carbon source, but still growing on glucose. Deletion mutants of Schw. occidentalis hexokinase prevented glucose repression of invertase and maltase. Growth deficiences and the defect of glucose repression of a S. cerevisiae hexokinase null mutant could be restored by heterologous expression of the Schw. occidentalis hexokinase. Moreover, the results clearly showed the existence of a separate glucokinase in Schw. occidentalis.
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  • 32
    ISSN: 1432-0983
    Keywords: Yeast ; Trehalose synthase ; GGS1/TPS1 gene ; Isogenic background ; Glucose transport ; Sporulation
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    Notes: Abstract The GGS1/TPS1 gene of the yeast Saccharomyces cerevisiae encodes the trehalose-6-phosphate synthase subunit of the trehalose synthase complex. Mutants defective in GGS1/TPS1 have been isolated repeatedly and they showed variable pleiotropic phenotypes, in particular with respect to trehalose content, ability to grow on fermentable sugars, glucose-induced signaling and sporulation capacity. We have introduced the fdp1, cif1, byp1 and glc6 alleles and the ggs1/tps1 deletion into three different wild-type strains, M5, SP1 and W303-1A. This set of strains will aid further studies on the molecular basis of the complex pleiotropic phenotypes of ggs1/tps1 mutants. The phenotypes conferred by specific alleles were clearly dependent on the genetic background and also differed for some of the alleles. Our results show that the lethality caused by single gene deletion in one genetic background can become undetectable in another background. The sporulation defect of ggs1/tps1 diploids was neither due to a deficiency in G1 arrest, nor to the inability to accumulate trehalose. Ggs1/tps1 Δ mutants were very sensitive to glucose and fructose, even in the presence of a 100-fold higher galactose concentration. Fifty-percent inhibition occurred at concentrations similar to the Km values of glucose and fructose transport. The inhibitory effect of glucose in the presence of a large excess of galactose argues against an overactive glycolytic flux as the cause of the growth defect. Deletion of genes of the glucose carrier family shifted the 50% growth inhibition to higher sugar concentrations. This finding allows for a novel approach to estimate the relevance of the many putative glucose carrier genes in S. cerevisiae. We also show that the GGS1/TPS1 gene product is not only required for the transition from respirative to fermentative metabolism but continuously during logarithmic growth on glucose, in spite of the absence of trehalose under such conditions.
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  • 33
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    Current genetics 28 (1995), S. 19-25 
    ISSN: 1432-0983
    Keywords: Ribosomal proteins ; Evolutionary relationships ; Yeast ; Intron
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    Notes: Abstract We previously reported the sequence of YL8A, one of the two genes encoding yeast ribosomal protein YL8. With the aim of conducting an evolutionary study we have cloned and sequenced a second gene, YL8B. The disruption of both genes is lethal. Unlike other duplicated ribosomal protein genes, each open reading frame is interrupted by two introns containing long conserved sequences. A comparison of nucleotide and amino-acid sequences reveals that the duplication of the YL8 gene must have occurred very recently. Alignment and phylogenetic analysis of the amino-acid sequences of YL8-related proteins from various species show the existence not only of YL8 ribosomal proteins but also of a family of YL8-like proteins. These are present in at least three species of yeast and seem to be functionally distinct from ribosomal proteins.
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  • 34
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    Current genetics 28 (1995), S. 499-501 
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; mgm ; Dynamin
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    Notes: Abstract Three previously described genes that affect baker's yeast (Saccharomyces cerevisiae) mitochondrial DNA (mtDNA) or mitochondrial RNA, tpm2-1, mnal-1, and mgml-1, are shown to be alleles of the same gene. This report demonstrates that tpm2-1 does not affect recombination of mtDNA. Therefore, there is no evidence that this dynamin-like protein is involved in movement of mtDNA within a cell.
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  • 35
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    Current genetics 28 (1995), S. 512-516 
    ISSN: 1432-0983
    Keywords: Yeast ; Saccharomyces ; Centromere ; Autonomously replicating segments
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    Notes: Abstract In this paper we report the cloning, sequencing and functional characterization of CEN12 and an associated autonomously replicating sequence (ARS) from the budding yeast Saccharomyces cerevisiae. In the course of studying a dynamin-related gene, DNM1, we previously physically mapped the gene to chromosome 12. Genetic mapping showed that the gene was tightly linked (0.35 cM) to the centromere. Subcloning experiments revealed that a centromerelike activity was included in a small segment of DNA immediately downstream from the DNM1 gene. Mitotic centromere activity was discerned by the ability of the region to de-stabilize a centromere-containing plasmid, and to stabilize an ARS-containing plasmid. Meiotic centromere activity was determined by the first-division segregation in crosses of ARS plasmids containing this region. The DNA sequence of this region revealed a sequence with strong homology to the consensus for yeast centromeres.
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  • 36
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    Current genetics 27 (1995), S. 95-101 
    ISSN: 1432-0983
    Keywords: mcm ; DNA replication ; RAD9 ; Yeast
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    Notes: Abstract The minichromosome maintenance mutation, mcm2-1, has been found to synthesize damaged DNA at 35°C. Growth at this temperature rendered the mutant strain more sensitive to killing by ultraviolet irradiation. DNA damage could also be detected by pulsed-field gel electrophoresis, where a higher fraction of the DNA loaded was retained in the inserts at the wells. During the exponential phase of growth at this temperature about 50% of the cells had large buds, with the nucleus at or near the neck of the bud in most cases. The incorporation of the rad9 deletion in the mcm2-1-carrying strain caused a reduction in the percentage of large-budded cells and a moderate loss of cell viability. The results are consistent with mcm2-1 causing DNA damage leading to the arrest of cells in the S/G2 phase of the cell cycle, which was partially dependent on the RAD9 gene product.
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  • 37
    ISSN: 1432-0983
    Keywords: Yeast ; Yarrowia lipolytica ; Protein secretion ; Rab protein
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    Notes: Abstract Small GTP-binding proteins of the Rab family are involved in the vesicular traffic inside eukaryotic cells. A gene library from the yeast Yarrowia lipolytica was screened with an oligonucleotide deduced from a highly conserved sequence in the Rab family. Four different genes were isolated. One of them, RYL1, was shown to be essential for cell viability. RYL1p displayed a high similarity with and tight phylogenetic relationships to SEC4p. When placed under the control of the GAL10 promoter, RYL1 was able to specifically relieve the thermosensitivity of a sec4–8 mutant of Saccharomyces cerevisiae. Therefore, it is proposed that RYL1 is a functional homologue of the S. cerevisiae SEC4 gene and is involved in the fusion of secretory vesicles with the plasma membrane in the general protein secretion pathway.
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  • 38
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    Archives of microbiology 107 (1976), S. 205-206 
    ISSN: 1432-072X
    Keywords: Torulopsis ; Yeast ; New species ; Beer
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    Topics: Biology
    Notes: Abstract A new species of the genus Torulopsis has been isolated from several different samples of German Pilsener Beer. A description of the new species is given.
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  • 39
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    Archives of microbiology 107 (1976), S. 299-302 
    ISSN: 1432-072X
    Keywords: Sulphite ; Sulphide ; ATP sulfurylase ; Pantothenate ; Yeast ; Fermentation
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    Notes: Abstract The influence of vitamin and cysteine supplementation on sulphite and sulphide formation, as well as on ATP sulfurylase activity, by two low-and two high-sulphite forming wine yeasts is examined using a defined synthetic fermentation substrate. The lowsulphite formers produce more sulphite in media lacking vitamins, whereas the high-sulphite formers produce less. One high-sulphite former has elevated ATP sulfurylase activity, but the other has activity similar to a low-sulphite forming strain. Only traces of sulphide are formed when the high-sulphite formers are grown with sulphate as the sulphur source, but considereable amounts are produced when cysteine is added to the medium. The low-sulphite formers produce H2S in the complete medium, and more is formed when vitamins are omitted.
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  • 40
    ISSN: 1432-072X
    Keywords: Mating tube ; Microtubule ; Tremella ; Ultrastructure ; Yeast
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    Notes: Abstract Ultrastructure of the mating tube formed in yeast haplont of the heterobasidiomycete Tremella mesenterica was studied by electron microscopy. Cell wall of the mating tube emerged as evagination of the inner layers, rupturing outer layers of the mother cell wall. Comparison with budding cells suggested that the tube emergence place at bud scar and the process of tube emergence was the same as that of bud emergence. Electron transparent vesicles of 0.1 μm diameter were scattered in the cytoplasm of the mating tube. Nucleus-associated organelle was located at one side of the nuclear envelope which extended towards the mating tube. A few microtubules were detected in the mating tube, but their association with a nucleus was not clear. The cytoplasmic structure of the mating tube was discussed in comparison with that of hyphae of the filamentous fungi.
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  • 41
    ISSN: 1432-072X
    Keywords: Hansenula polymorpha ; Yeast ; Peroxisomes ; Proton-translocating ATPase ; Cell fractionation ; Fluorescence quenching studies ; Cytochemistry
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    Notes: Abstract The association of an ATPase with the yeast peroxisomal membrane was established by both biochemical and cytochemical procedures. Peroxisomes were purified from protoplast homogenates of the methanol-grown yeast Hansenula polymorpha by differential and sucrose gradient centrifugation. Biochemical analysis revealed that ATPase activity was associated with the peroxisomal peak fractions which were identified on the basis of alcohol oxidase and catalase activity. The properties of this ATPase closely resembled those of the mitochondrial ATPase of this yeast. The enzyme was Mg2+-dependent, had a pH optimum of approximately 8.5 and was sensitive to N,N′-dicyclohexylcarbodiimide (DCCD), oligomycin and azide, but not to vanadate. A major difference was the apparent K m for ATP which was 4–6 mM for the peroxisomal ATPase compared to 0.6–0.9 mM for the mitochondrial enzyme. Cytochemical experiments indicated that the peroxisomal ATPase was associated with the membranes surrounding these organelles. After incubations with CeCl3 and ATP specific reaction products were localized on the peroxisomal membrane, both when unfixed isolated peroxisomes or formaldehyde-fixed protoplasts were used. This staining was strictly ATP-dependent; in controls performed i) in the absence of substrate, ii) in the presence of glycerol 2-phosphate instead of ATP, or iii) in the presence of DCCD, staining was invariably absent. Similar staining patterns were observed in subcellular fractions and protoplasts of Candida utilis and Trichosporon cutaneum X4, grown in the presence of ethanol/ethylamine or ethylamine, respectively.
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  • 42
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    Archives of microbiology 147 (1987), S. 105-108 
    ISSN: 1432-072X
    Keywords: Ozone ; Yeast ; Saccharomyces cerevisiae ; ATP ; Nucleotides ; Permeability ; Cytosolic enzymes
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    Topics: Biology
    Notes: Abstract Treatment of a yeast suspension with ozone inactivates a number of cytosolic enzymes. Among 15 studied, the most drastic inactivation was found for glyceraldehyde-3-phosphate dehydrogenase and to lesser extents: NAD-glutamate dehydrogenase, pyruvate decarboxylase, phosphofructokinase-1 and NAD-alcohol dehydrogenase. Ozone treatment also effects the quantity of ATP and of other nucleoside triphosphates, reducing to about 50% of the initial value. The ATP missing in the cells appears in the medium. NAD and protein also accumulate in the medium suggesting that the yeast cells have been permeabilized. Permeabilization of the yeast cells by treatment with ozone preceeds the inactivation of glyceraldehyde-3-phosphate dehydrogenase and other cytosolic enzymes.
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  • 43
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    Archives of microbiology 147 (1987), S. 235-239 
    ISSN: 1432-072X
    Keywords: Chloroquine ; Yeast ; Fructose-1,6-bisphosphatase ; Phosphorylation ; Protein kinase
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    Notes: Abstract The rapid phase of fructose-1,6-bisphosphatase (FBPase) inactivation following glucose addition to starved yeast cells [reported previously] is inhibited on addition of 10 mM chloroquine (CQ) at about pH 8. This inhibition of inactivation was shown to be due to the prevention of phosphorylation of the enzyme. CQ was also found to inhibit general protein phosphorylation in the yeast cells. Glycolysis, as observed by changes in intracellular glucose-6-phosphate and extracellular glucose and ethanol concentrations, was shown to be significantly inhibited in cells treated with CQ. Similarly, a decrease in ATP concentrations was observed. However, during the early stages of phosphorylation of FBPase, levels of ATP were similar in cells containing CQ as in those without CQ. Thus, decrease in ATP levels is not thought to be significantly responsible for the inhibition of protein phosphorylation. However, the phosphorylating activity of cyclic AMP-dependent protein kinases is inhibited in vitro by relatively low concentrations of CQ. Thus, prevention of protein phosphorylation by CQ is believed to be due to inhibition of protein kinases in yeast cells.
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  • 44
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    Archives of microbiology 109 (1976), S. 153-156 
    ISSN: 1432-072X
    Keywords: Yeast ; Taxonomy ; Kluyveromyces
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    Description / Table of Contents: Zusammenfassung Eine neue Hefe der Gattung Kluyveromyces konnte aus dem Darmtrakt einer Küchenschabe (Blatta orientalis) isoliert werden. Die Hefe wird neu beschrieben und eine lateinische Diagnose gegeben.
    Notes: Abstract A new hitherto undescribed species of yeast of the genus Kluyveromyces has been isolated from the intestinal tract of the oriental cockroach (Blatta orientalis). A description of the new species including latin diagnosis is given.
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  • 45
    ISSN: 1432-072X
    Keywords: Iron ; Cyanide-resistance ; Hydroxamates ; Alternative respiration ; Yeast ; Saccharomycopsis lipolytica
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    Notes: Abstract The specific inhibitory effect of benzhydroxamic acid on the cyanide-insensitive respiration could be reversed in whole cells of the yeast Saccharomycopsis lipolytica, by addition of Fe(III), in a way suggesting a competition between the added iron and an enzyme-bound metallic ion, both central atoms for the ligand benzhydroxamic acid. The possibility that added metal ions modify the penetration of BHAM into the cells was ruled out. Co(II), Cu(II) and Al(III) could substitute for Fe(III). A linear relation between the concentration in added Fe(III) and the reversed respiration rate was observed. At a given cell concentration. the reversion by added Fe(III) of the inhibitory effect of benzhydroxamic acid on the alternative respiration appeared more related to the degree of inhibition rather than to the concentration in added inhibitor. Increasing cell concentrations required increasing amounts of Fe(III) to reach the same level of reversion. No reversal occurred at concentrations in added Fe(III) lower than 0.1 mM, whatever the benzhydroxamic concentration, the cell concentration or the yeast batch.
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  • 46
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    Archives of microbiology 109 (1976), S. 85-88 
    ISSN: 1432-072X
    Keywords: Sulphate ; Sulphite ; Sulphite reductase ; ATP sulfurylase ; Fermentation ; Yeast
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    Topics: Biology
    Notes: Abstract Sulphite reductase and ATP sulfurylase activities were compared in low- and high-sulphite forming wine yeasts grown in a synthetic medium. Reduced nicotinamide adenine dinucleotide phosphate-linked sulphite reductase activity was not detected in extracts from high-sulphite forming yeasts, although high activity was found in extracts from low-sulphite formers. High-sulphite forming yeasts had elevated ATP sulfurylase activity compared to the low-sulphite formers indicating derepression of enzyme synthesis. A high rate of activation and reduction of sulphate to sulphite was considered the main factor responsible for the accumulation of sulphite by high-sulphite forming wine yeasts. Over a 5-day fermentation period, sulphite accumulation in the growth medium by low-sulphite forming yeasts was correlated with ATP sulfurylase activity.
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  • 47
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    Archives of microbiology 111 (1976), S. 197-198 
    ISSN: 1432-072X
    Keywords: Enzyme regulation ; Ornithine transcarbamylase ; OTC ; Rhodotorula glutinis ; Ropression ; Yeast ; Arginine biosynthesis ; Citrulline biosynthesis ; Metabolic regulation ; Amino acid metabolism
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The regulation of ornithine transcarbamylase (OTC) of Rhodotorula glutinis has been studied, by growing the yeasts in different carbon and nitrogen sources and estimating the enzyme level in crude yeasts extracts. The results show a nutritional repression of OTC by arginine, when added to the culture media as carbon, nitrogen or carbon and nitrogen sources. On the other hand ornithine does not exert any effect in the same experimental conditions.
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  • 48
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    Archives of microbiology 109 (1976), S. 115-118 
    ISSN: 1432-072X
    Keywords: Yeast ; Protoplasts ; Vacuoles ; Concanavalin A ; Membrane asymmetry
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    Notes: Abstract Isolated vacuoles of Saccharomyces cerevisiae did not bind Concanavalin A (labelled with tritium or with a fluorescent dye) unless the vacuoles were rendered permeable and their inner membrane surface made accessible. Yeast protoplasts, on the other hand, bound large amounts of Concanavalin A on their surface, and the number of binding sites was not increased after a gentle lysis expected to expose also the inner surface of the plasmalemma. It is concluded that both the plasmalemma and the vacuolar membrane carry Concanavalin A binding sites exclusively on the surface opposite to the cytoplasmic matrix.
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  • 49
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    Archives of microbiology 108 (1976), S. 293-298 
    ISSN: 1432-072X
    Keywords: Yeast ; Saccharomyces cerevisiae ; Maximum temperature for growth ; Thermal death ; Linear thermodynamic compensation ; Non-linear thermodynamic compensation ; Isokinetic temperature
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    Topics: Biology
    Notes: Abstract Sixty eight Arrhenius plots of thermal death in six mesophilic yeast species, tested at various concentrations of NaCl, lacked an isokinetic temperature. Nevertheless the ΔH #/ΔS # plot was apparently linear with a slope corresponding to 314° K. It was concluded that linear thermodynamic compensation of thermal death is non-existent in heterogeneous groups of yeasts and is unlikely to occur in heterogeneous groups of other organisms and that ΔH #/ΔS # plots lack sensitivity for the detection of non-linearity over narrow temperature ranges. However, the ΔH # and ΔS # parameters of thermal death displayed non-linear compensation in such a way that the extrapolated Arrhenius plots of death attained nearly identical values near the respective maximum temperatures for growth. Linear thermodynamic compensation occurred in each of the six strains, when stationary populations of the same strain were tested at various NaCl concentrations. On the other hand, exponential populations of each of the strains, tested in the same way, lacked an isokinetic temperature of thermal death. The significance of linear and non-linear thermodynamic compensation in biological rate processes is discussed.
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  • 50
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    Archives of microbiology 111 (1976), S. 193-194 
    ISSN: 1432-072X
    Keywords: Yeast ; d-glucose ; Transport ; Uptake ; Kinetics ; Candida utilis
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    Topics: Biology
    Notes: Abstract Unlike other yeasts so far investigated, the d-glucose carrier of Candida utilis (strain NCYC 737) appears to change affinity for d-glucose according to its exogenous concentration. When the concentration of d-glucose was 〈0.4 mM, the apparent K m≈ 0.2 mM; at 〉0.4 mM, the K m≈ 10 mM.
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  • 51
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    Archives of microbiology 115 (1977), S. 1-7 
    ISSN: 1432-072X
    Keywords: Cell walls ; Chitin ; Colloidal gold ; Concanavalin A ; Cytochemistry ; Mannan ; Wheat germ agglutinin ; Yeast ; Saccharomyces cerevisiae ; Candida utilis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mannan was located on thin sections of Saccharomyces cerevisiae and Candida utilis with the homologous anti-mannan antibodies or with Concanavalin A, both labelled with gold granules. Fully synthesized mannan was found in the cell walls, on the plasmalemma and within the cytoplasm sometimes associated with vesicles and vacuoles. Chitin or its oligomers were located with wheat germ agglutinin in the bud scars but also in the cell wall and the cytoplasm near the plasmalemma. Both mannan and chitin or its oligomers were found in the forming septum and are synthesized within the cytoplasm. The gold method was also suitable for marking mannan and chitin simultaneously.
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  • 52
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    Archives of microbiology 124 (1980), S. 285-287 
    ISSN: 1432-072X
    Keywords: Yeast ; Saccharomyces cerevisiae ; Heat killing ; Membrane damage ; Genetic damage ; Growth temperature
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    Topics: Biology
    Notes: Abstract The resistance of exponentially growing yeast cells to killing by exposure to 52°C increased markedly as the growth temperature was increased. Identical killing curves were obtained for cells suspended in growth medium or in 0.9% saline. Cells resistant to killing at 52°C were quite sensitive to killing at slightly higher temperatures. These results suggest a primary role for membrane damage in the mechanism of heat killing.
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  • 53
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    Journal of industrial microbiology and biotechnology 14 (1995), S. 164-168 
    ISSN: 1476-5535
    Keywords: Nickel ; Resistance ; Yeast ; Fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary This review describes nickel toxicity and nickel resistance mechanisms in fungi. Nickel toxicity in fungi is influenced by environmental factors such as pH, temperature and the existence of organic matter and other ions. We describe resistance mechanisms in nickel-resistant mutants of yeasts and filamentous fungi which were obtained by exposure to a mutagen or by successive culture in media containing increasing concentrations of nickel ion. Nickel resistance may involve: (1) inactivation of nickel toxicity by the production of extracellular nickel-chelating substances such as glutathione; (2) reduced nickel accumulation, probably by modification of a magnesium transport system; (3) sequestration of nickel into a vacuole associated with free histidine and involving Ni-insensitivity of vacuolar membrane H+-ATPase.
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  • 54
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    Journal of industrial microbiology and biotechnology 2 (1987), S. 59-62 
    ISSN: 1476-5535
    Keywords: Yeast ; Zygosaccharomyces ; Spoilage ; Synergism ; pH ; °Brix
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A quantitative method for the prediction of growth of the food spoilage yeastZygosaccharomyces bailii in a model fruit-drink system is described. A factorially designed experiment was employed to produce polynomial equations relating pH and sugar concentration (°brix) to the lag period and doubling time of this yeast. Low pH values (〈3.0) and high °brix values (〉40) show a strong synergistic action on the extension of lag period, which could be used, along with the model presented, in the formulation of product preservation systems.
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  • 55
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    Journal of industrial microbiology and biotechnology 2 (1987), S. 159-165 
    ISSN: 1476-5535
    Keywords: Yeast ; Genetic stability ; Saccharomyces cerevisiae ; Selection ; Reproductive fitness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The potential for changes in allele frequencies in yeast populations by selection was examined. Cells from the wine yeastSaccharomyces cerevisiae (strain Montrachet) were grown over a large number of generations using two different culturing techniques, each with two variations: serial transfers on WLN agar plates with and without UV irradiation, and continuous culture in autoclaved and in filter-sterilized grape must. A low frequency of variant isozyme patterns was found in samples taken at the end of the experiment. Growth rates in must and on agar plates were also examined, and it was found that all samples were faster-growing than the original strain, to varying degrees. Applications for the selection system developed are discussed.
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  • 56
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    Molecular genetics and genomics 249 (1995), S. 209-216 
    ISSN: 1617-4623
    Keywords: Yeast ; Cell wall ; β-Glucan synthesis ; Kre1p ; O-glycoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Saccharomyces cerevisiae KRE1 gene encodes a secretory protein required for the production of the cell wall polymer (1 → 6)-β-glucan. Here we report further characterization of the KRE1 gene product, Krelp. A functional, epitope-tagged Krelp is shown to be highly modified in a SEC53-dependent manner. Krelp is O-glycosylated, but the basis for the majority of its post-translational modification is unknown. Fractionation of Kre1p reveals a cell wall-associated form and a less abundant membrane-associated species. Indirect immunoflurorescence demonstrates that Kre1p localizes to the cell surface, where it becomes concentrated at the surface of mother cells. Such a localization of Kre1p seems to parallel the CAL1/CSD2-dependent cell wall deposition of chitin found in S. cerevisiae, and is consistent with evidence from Schizophyllum commune that (1 → 6)-β-glucan accumulates during maturation of the subapical region of the wall distal to the hyphal tip.
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  • 57
    ISSN: 1617-4623
    Keywords: Calcineurin ; Protein kinase A ; Na+ pump ; Salt tolerance ; Yeast
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    Topics: Biology
    Notes: Abstract Ca2−/calmodulin-dependent phosphoprotein phosphatase (calcineurin, PP2B) of Saccharomyces cerevisiae is implicated in adaptation to high-salt conditions. Calcineurin mediates high salt-induced expression of the ENA1/PMR2 gene encoding the P-type ATPase, which is suggested to be involved in Na+ efflux. We identified the PDE1 gene encoding the low-affinity cAMP phosphodiesterase as a multicopy suppressor of the Li+- and Na+-sensitive calcineurin null mutant, suggesting that cAMP is a negative regulator of adaptation to high-salt stress. Genetic analysis indicated that calcineurin and cAMP act antagonistically in a common pathway for adaptation. The bcy1 disruption, which leads to constitutive cAMP-dependent protein kinase (PKA) activity, inhibited high NaCl-induced expression of the ENA1/PMR2 gene, caused an elevation of the intracellular Na+ level and a growth defect in high-NaCl medium, all of which were analogous to the defects of a calcineurin mutant. A reduced cAMP level resulting from multiple copies of the PDE1 gene caused increased expression of the ENA1/PMR2 gene in response to high NaCl. We propose a model for the regulation of cation homeostasis, in which calcineurin antagonizes PKA to activate transcription of the ENA1/PMR2 gene in response to high-salt conditions.
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  • 58
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    Molecular genetics and genomics 249 (1995), S. 309-316 
    ISSN: 1617-4623
    Keywords: Meiosis ; Chromosome segregation ; Ring chromosome ; Artificial chromosome ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Meiotic chromosome segregation must occur with high fidelity in order to prevent the generation of aneuploid cells. We have previously described the identification and genetic characterization of a yeast mutant with defects in meiotic sister-chromatid segregation. We attributed the phenotype in this mutant to a dominant allele, which we referred to as SID1-1. These mutants appeared to exhibit high levels of nondisjunction and precocious separation of sister-chromatids of chromosome III, as well as precocious separation of sister chromatids of chromosome VIII and a univalent artificial chromosome. We show here that the unusual meiotic behavior of chromosome III in these strains is due to the presence of a ring III chromosome, rather than a mutant gene. Additional experiments demonstrate that a ring III/rod III pair alters the meiotic segregation of a univalent artificial chromosome.
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  • 59
    ISSN: 1617-4623
    Keywords: Yeast ; Kluyveromyces lactis ; Alcohol dehydrogenase ; Glucose and ethanol metabolism ; Transcriptional regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The lactose-utilizing yeast Kluyveromyces lactis is an essentially aerobic organism in which both respiration and fermentation can coexist depending on the sugar concentration. Despite a low fermentative capacity as compared to Saccharomyces cerevisiae, four structural genes encoding alcohol dehydrogenase (ADH) activities are present in this yeast. Two of these activities, namely KlADH III and KlADH IV, are located within mitochondria and their presence is dependent on the carbon sources in the medium. In this paper we demonstrate by transcription and activity analysis that KlADH3 is expressed in the presence of low glucose concentrations and in the presence of respiratory carbon sources other than ethanol. Indeed ethanol acts as a strong repressor of this gene. On the other hand, KlADH4 is induced by the presence of ethanol and not by other respiratory carbon sources. We also demonstrate that the presence of KlADH III and KlADH IV in K. lactis cells is dependent on glucose concentration, glucose uptake and the amount of ethanol produced. As a consequence, these activities can be used as markers for the onset of respiratory and fermentative metabolism in this yeast.
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  • 60
    ISSN: 1617-4623
    Keywords: Yeast ; Sulphate transport ; Sulphate uptake ; Mutagenesis
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    Topics: Biology
    Notes: Abstract Resistance to selenate and chromate, toxic analogues of sulphate, was used to isolate a mutant of Saccharomyces cerevisiae deficient in the capacity to transport sulphate into the cells. A clone which complements this mutation was isolated from a cDNA library prepared from S. cerevisiae poly(A)+ RNA. This clone contains an insert which is 2775 by in length and has a single open reading frame that encodes a 859 amino acid polypeptide with a molecular mass of 96 kDa. Sequence motifs within the deduced amino acid sequence of this cDNA (SUL1) show homology with conserved areas of sulphate transport proteins from other organisms. Sequence analysis predicts the position of 12 putative membrane spanning domains in SUL1. When the cDNA for SUL1 was expressed in S. cerevisiae, a high affinity sulphate uptake activity (Km = 7.5 ± 0.6 μM for SO 4 2− ) was observed. A genomic mutant of S. cerevisiae in which 1096 by were deleted from the SUL1 coding region was constructed. This mutant was unable to grow on media containing less than 5 mM sulphate unless complemented with a plasmid containing the SUL1 cDNA. We conclude that the SUL1 cDNA encodes a S. cerevisiae high affinity sulphate transporter that is responsible for the transfer of sulphate across the plasma membrane from the external medium.
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  • 61
    ISSN: 1617-4623
    Keywords: Chloramphenicol resistance ; frameshifting Mitochondria ; 21S rRNA ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mutation shown to cause resistance to chloramphenicol inSaccharomyces cerevisiae was mapped to the central loop in domain V of the yeast mitochondrial 21S rRNA. The mutant 21S rRNA has a base pair exchange from U2677 (corresponding to U2504 inEscherichia coli) to C2677, which significantly reduces rightward frameshifting at a UU UUU UCC A site in a + 1 U mutant. There is evidence to suggest that this reduction also applies to leftward frameshifting at the same site in a − 1 U mutant. The mutation did not increase the rate of misreading of a number of mitochondrial missense, nonsense or frameshift (of both signs) mutations, and did not adversely affect the synthesis of wild-type mitochondrial gene products. It is suggested here that ribosomes bearing either the C2677 mutation or its wild-type allele may behave identically during normal decoding and only differ at sites where a ribosomal stall, by permitting non-standard decoding, differentially affects the normal interaction of tRNAs with the chloramphenicol resistant domain V. Chloramphenicol-resistant mutations mapping at two other sites in domain V are described. These mutations had no effect on frameshifting.
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  • 62
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    Molecular genetics and genomics 207 (1987), S. 320-327 
    ISSN: 1617-4623
    Keywords: Cell cycle ; DNA damage ; Carcinogenesis ; Yeast ; cdc2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pedigree analyses of individual yeast cells recovering from DNA damage were performed and time intervals between morphological landmark events during the cell cycle (bud emergence and cell separation), were recorded for three generations. The associated nuclear behavior was monitored with the aid of DAPI staining. The following observations were made: (1) All agents tested (X-rays, MMS, EMS, MNNG, nitrous acid) delayed the first bud emergence after treatment, which indicates inhibition of the initiation of DNA replication. (2) Cells that survived X-irradiation progressed further through the cell cycle in a similar way to control cells. (3) Progress of chemically treated cells became extremely asynchronous because surviving cells stayed undivided for periods of varying length. (4) Prolongation of the time between bud emergence and cell separation was most pronounced for cells treated with the alkylating agents MMS and EMS. This is interpreted as retardation of ongoing DNA synthesis by persisting DNA adducts. (5) Cell cycle prolongation in the second and third generation after treatment was observed only with MMS treated cells. (6) In all experiments, individual cells of uniformly treated populations exhibited highly variable responses.
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  • 63
    ISSN: 1617-4623
    Keywords: Yeast ; Ty-VLPs ; Ty-encoded functions ; Processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have analysed functional properties of putative proteins encoded by the yeast transposable element, Ty1, by overexpression of TY genes. High-level expression was achieved by appropriate fusion of a Ty sequence, TY9C, to the yeast ADH1 promoter and transformation of yeast cells with this construction. As shown recently by others (Garfinkel et al. 1985; Mellor et al. 1985c) TY over-expression leads to an increase in particle-bound reverse transcriptase activity and to an intracellular accumulation of virus-like particles (Ty-VLPs). We have used a number of deletions in the second open reading frame (TYB) to identify functional domains required for processing and assembly of Ty proteins. Deletions in the TYB region with homology to acid proteases result in overproduction of an unprocessed form of the TYA protein (pro-TYA) which represents the major protein of Ty-VLPs. One particular mutant construction, TY9C-Δ36, led to the accumulation of a particle-bound, 160 kDa protein which cross-reacted with a mouse antiserum raised against purified pro-TYA protein. This supports the hypothesis that TYB is expressed as a TYA/TYB fusion protein which is processed by a TYB-encoded protease activity. Ty-VLPs are formed in the absence of protein processing and even when the TYB gene is not expressed. Thus, we assume that the assembly of Ty particles occurs prior to processing of Ty proteins.
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  • 64
    ISSN: 1617-4623
    Keywords: Yeast ; Permease ; LAC12
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutants of Kluyveromyces lactis defective in lactose transport were identified among lactose-resistant revertants of lactose-sensitive strains. The mutations are closely linked to the β-galactosidase gene, LAC4, and they are located in a previously identified gene, LAC12, which has been shown to code for a lactose permease. Our data establish that LAC12 is the only lactose permease gene in K. lactis. The lactose permease also transports galactose. LAC12 is transcribed in a direction opposite to that of LAC4, there being about 2.5 kb between their transcription start sites. Transcription of LAC12 is inducible as is that of all other structural genes in the lactose-galactose regulon of K. lactis.
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  • 65
    ISSN: 1617-4623
    Keywords: General control ; Gene regulation ; HIS5 ; Saccharomyces cerevisiae ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nucleotide sequence of a 2.1 kb DNA fragment bearing the HIS5 gene of Saccharomyces cerevisiae, which encodes histidinol-phosphate aminotransferase (EC 2.6.1.9), has been determined. An open reading frame of 1,152 bp was found. S1 nuclease mapping indicated that the major transcription starts at position-37 from the ATG codon and the minor (∼20%) at-34 in both repressive and derepressive conditions. Northern analysis indicated that transcription of the HIS5 gene is under the general control of amino acid biosynthesis. The 5′ noncoding region of the gene, thus far examined up to position-616, contains three copies of sequences homologous to the short repeats of the consensus sequence, 5′-A T A GTGACTC-3′, suggested for general amino acid control in the HIS1, HIS3, HIS4, and TRP5 at positions-336,-275 and-205. The consensus sequence closest to the open reading frame was shown to be necessary but not sufficient for general amino acid control, by examination of β-galactosidase appearance in S. cerevisiae cells carrying various mutant HIS5 promoter regions fused to the lac'Z gene and inserted at the leu2 locus of chromosome III.
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  • 66
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    Molecular genetics and genomics 206 (1987), S. 377-381 
    ISSN: 1617-4623
    Keywords: Yeast ; Saccharomyces kluyveri ; Linear plasmid ; Terminal protein ; Inverted terminal repetition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new linear DNA plasmid, designated pSKL, was found in the yeast Saccharomyces kluyveri. Restriction maps of the 14.2 kb plasmid were constructed. By the use of CsCl-Hoechst 33258 centrifugation containing guanidine chloride, pSKL was isolated as a DNA-protein complex. The protein was associated with the terminal regions of pSKL. The two terminal EcoRI fragments of pSKL were cloned and their nucleotide sequences were determined. pSKL had inverted terminal repeats of 483 bp with a unique structure in which fairly homologous sequences of 30 bp were repeated eight times.
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  • 67
    ISSN: 1617-4623
    Keywords: Yeast ; Mitochondrial tRNA ; syn - mutation ; Mitochondrial protein synthesis ; tRNA structure-function relationship
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial temperature-sensitive mutation tsm-8 maps on a 1.8 kb HpaII fragment of mitochondrial DNA (mt DNA) which contains genes for tRNAAla, tRNAIle and tRNATyr. The phenotype of this mutation is, among multiple pleiotropic defects, a temperature-induced reduction of mitochondrial translation. DNA sequencing of the HpaII fragment from the wild type and mutant tsm-8 revealed a single transversion from T to A in position 56 of the mutant tRNATyr gene. This nucleotide change disrupts a base pairing in the long extra arm of the tRNA cloverleaf. Revertants of the tsm-8 mutant restore correct base pairing in the extra arm by a second-site mutation in the tRNATyr gene. Analysis of the tRNATyr transcripts revealed that neither transcription nor processing of the tRNA is affected in the mutant. However, the base alteration destabilizes the conformation of the tRNA and affects its charging parameters. At the non-permissive temperature, the Michaelis-Menten constant of the mitochondrial tyrosyl-tRNA synthetase for the mutant tRNA is increased over 20-fold when compared to the wild-type tRNA. As a consequence, mitochondrial protein synthesis is drastically reduced at the restrictive temperature. Moreover, synthesis of apocytochrome b and of cytochrome oxidase subunit 3 is decreased relative to the other mitochondrially synthesized polypeptides.
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  • 68
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    Molecular genetics and genomics 207 (1987), S. 161-164 
    ISSN: 1617-4623
    Keywords: Origin of replication ; ARS ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A DNA sequence has been isolated from Schizosaccharomyces pombe which promotes high frequency transformation of plasmids in the same organism. It is closely linked to the DNA ligase gene CDC17 and has therefore been named ARS17 although in structure it differs substantially from ARS elements in Saccharomyces cerevisiae. ARS17 spans some 1.8 kb of DNA and deletion of any part of this region affects activity. Moreover, there does not appear to be any short sequence which is, by itself, sufficient for high frequency transformation. ARS17 lies between and partly overlaps two divergently transcribed genes and it is extremely AT rich. It lacks the consensus sequence found in S. cerevisiae ARSs and it has no ARS activity in S. cerevisiae.
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  • 69
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    Molecular genetics and genomics 246 (1995), S. 445-454 
    ISSN: 1617-4623
    Keywords: Yeast ; Cytochrome oxidase ; Mitochondria ; Intronic proteins ; Ribozymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have analysed the precise location of a large number (170) of mutations affecting the structural gene for subunit 1 of the cytochrome c oxidase complex. This gene, COXI, is 12.9 kb long and the major part of the sequence (i.e. 11.3 kb) is composed of introns. Several conclusions can be drawn from this study: (1) A significant proportion (84/170) of the mutations cannot be assigned to a single position within the gene by deletion mapping, in spite of clearly being located in it. These mutations are probably large deletions or multiple mutations. (2) Four mutants carry distant double mutations, which have been individually localized. (3) Eighty-two mutants have lesions that are restricted to very short regions of the gene and we therefore conclude that they are most probably due to single hits; amongst these single mutations, 41 are unambiguously located in exons and 28 in introns. This result implies that, at least in this particular split gene, the probability of selection of a mutant phenotype in an exon is, on the average, 13.3 times greater than in an intron, in spite of the existence, within most of these introns, of open reading frames specifying intronic proteins. The evolutionary significance and biological implications of these results are discussed.
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    Molecular genetics and genomics 248 (1995), S. 229-235 
    ISSN: 1617-4623
    Keywords: Yeast ; Transcription ; HAP1 ; Heme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity of the yeast activator HAP1in vivo requires heme. A heme responsive domain of HAP1 was identified previously. It is adjacent to the DNA-binding domain, and appears to block DNA binding in the absence of heme. Here we describe a novel genetic selection which yielded mutants of HAP1 that are independent of heme when assayed for activation. These mutants define a second region of HAP1, close to the activation domain, which also controls its response to heme.
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    Molecular genetics and genomics 246 (1995), S. 236-246 
    ISSN: 1617-4623
    Keywords: Yeast ; K28 killer toxin ; cDNA expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The killer toxin K28, secreted by certain killer strains of the yeast Saccharomyces cerevisiae is genetically encoded by a 1.9 kb double-stranded RNA, M-dsRNA (M28), that is present within the cell as a cytoplasmically inherited virus-like particle (VLP). For stable maintenance and replication, M28-VLPs depend on a second dsRNA virus (LA), which has been shown to encode the major capsid protein (cap) and a capsidpolymerase fusion protein (cap-pol) that provides the toxin-coding M-satellites with their transcription and replicase functions. K28 toxin-coding M28-VLPs were isolated, purified and used in vitro for the synthesis of the single-stranded M28 transcript, which was shown to be of plus strand polarity and to bind to oligo(dT)-cellulose, indicating that M28(+)ssRNA contains an internal A-rich tract. Strand separation of the 1.9 kb M28-dsRNA and direct RNA sequencing of its 3′ ends was performed in order to obtain specific DNA oligonucleotides that could be used as primers for cDNA synthesis. The nucleotide sequence of the toxin-coding M28-cDNA identified a single open reading frame (ORF) coding for a polypeptide of 345 amino acids, which contained two potential Kex2p/Kex1p processing sites and three potential sites for protein N-glycosylation. The toxin-coding cDNA was cloned and expressed in sensitive non-killer strains under the control of the yeast PGK promoter. Upon transformation, this construct conferred the complete K28 phenotype, demonstrating that both toxin and immunity determinants are contained within the cloned cDNA. In vitro translational analysis of the M28(+)ssRNA in vitro transcript identified the primary gene product of M28 as a K28 preprotoxin of 38 kDa (M-p38).
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  • 72
    ISSN: 1617-4623
    Keywords: STA1 UASI ; Transcriptional regulation ; Glucoamylase ; STA10 ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has been reported that two upstream activation sites, UASI and UAS2, exist in the 5′ non-coding region of the STA1 gene of Saccharomyces cerevisiae var. diastaticus. Based on studies using a UAS1STA1-CYCI-lacZ fusion, we divided UASI into two subsites, UASI-1 and UASI-2. The activation of the CYC1 promoter by UAS1STA1 was repressed by glucose in the culture medium and by the STA10 gene. The MAT a/MATα mating type configuration did not, however, affect UAS1STA1 activation. The UAS1STA1-CYC1-lacZ expression system was used to study STA10 repression further. A mutant insensitive to STA10-dependent repression was isolated. This sns1 mutation was not linked to STA10 and partially overcame the repressive effect of STA10 at the transcriptional level. From a genomic library constructed in the UAS1STA1-CYC1-lacZ expression vector, the MSS1 locus (multicopy suppressor of sns1) was isolated. This suppression of the sns1 mutation by multiple copies of the mss1 locus occurred at the transcriptional level. When a gene disruption experiment was performed to examine the effect of a mss1 mutation, the sns1 mss1 double mutants produced 4 times higher levels of STA1 transcripts in the presence of STA10 than did the sns1 strain. Data presented in this paper suggest that both SNS1 and MSS1 loci are involved in STA10-dependent repression.
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  • 73
    ISSN: 1617-4623
    Keywords: PHO84 ; Phosphatase regulon ; Upstream activation site ; Yeast
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    Topics: Biology
    Notes: Abstract Transcription of the PHO84 gene encoding a Pi transporter in Saccharomyces cerevisiae is regulated by the Pi concentration in the medium. The promoter region of PHO84 bears five copies of the motif 5′-CACGT(G/T)-3′, a candidate for the upstream activation site (UAS) that binds the transcriptional activator protein of the phosphatase regulon, Pho4p. These motifs are found at nucleotides - 880 (site A), —587 (B), - 436 (C), - 414 (D), and - 262 (E) relative to the putative ATG codon of PHO84. The Pho4p protein binds to all five 6-bp motifs with various affinities. Deletion analysis of the PHO84 promoter using a PHO84-lacZ fusion gene and base substitutions in the 6-bp motif revealed that two copies of the 6-bp motif, either C or D, and E, are necessary and sufficient for full regulation of the PHO84 gene. Results of expression studies with a CYC1-lacZ fusion gene with various 36-bp oligonucleotides including the 30-bp sequences around site D or E, or with modified sequences, inserted in the CYC1 promoter region indicated that the 6-bp motif flanked by a thymine nucleotide at its 5′ end is much less effective as a UAS site for Pho4p in vivo than other versions. Thus, the consensus sequences for phosphatase regulation are 5′-GCACGTGGG-3′ and 5′-GCACGTTTT-3′ which differ from the binding sequences for the Cpflp protein required for transcription of the genes in methionine biosynthesis and for centromere function. However, Pho4p binding in vitro was unaffected by modification of the 5′ or 3' flanking sites of the 6-bp motif, while modification inside the 6-bp motif affected it severely. The UAS function of the GCACGTTTT motif with respect to the Pi signal depends on its orientation in the promoter sequence.
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  • 74
    ISSN: 1617-4623
    Keywords: Basal transcription ; BEL2/SIN4/TSF3 gene ; GCN4 ; PHO4 ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two single (bel2 and bel4) and two double (bel3 bel7 and bel5 bel6) mutations causing enhanced transcription of a gene fusion, consisting of the open reading frame of PHO5 connected to the HIS5 promoter (HIS5p) integrated at the ura3 or leu2 locus, were isolated from a gcn4-disrupted mutant of Saccharomyces cerevisiae. The PHO5 gene, encoding repressible acid phosphatase, in the HIS5p-PHO5 construct was derepressed under amino acid starved conditions by the action of the transcriptional activator Gcn4p. The bel mutants showed temperature-sensitive cell growth and/or cell aggregation. All the mutants except bel4 also showed high levels of transcription of an intact PHO5 DNA integrated at the URA3 locus in the absence of the cognate transcriptional activator, Pho4p, and in the absence of upstream activating sequences of PHO5. The HIS5 and PHO5 genes at their original chromosomal positions were, however, not affected by the bel2 mutation. The BEL2 gene was found to be identical with SIN4/TSF3, mutations in which cause high levels of transcription of the HO and GAL genes in the absence of their respective transcriptional activators, Swi5p and Gal4p. The effect of the bel2/sin4/tsf3 mutation on PHO5 transcription was additive with the Pho4p function. Thus the effect of the bel2/sin4/tsf3 mutation is dependent on the position of PHO5 in the chromosome and independent of Pho4p and Gen4p activation.
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  • 75
    ISSN: 1617-4623
    Keywords: Gene regulation ; Transcriptional activator ; Sucrose carrier ; Invertase ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A yeast strain deficient in secreted invertase but expressing a cytoplasmic sucrose synthase has been used to select for potato genes that enable growth on sucrose as the sole carbon source by suppressing the sucrose uptake deficiency. Besides the already known sucrose transporter gene (StSUT1), ten different suppressor clones were identified and characterized. One of these cDNAs (PCP1) enabled efficient growth of the mutant yeast strain and mediated uptake of radiolabelled sucrose. The cDNA encodes a protein of 509 amino acids which is highly hydrophilic and thus does not seem to represent a transporter. Sequence comparisons show that the protein contains zinc finger motifs and shares weak homologies with the Drosophila couch potato gene, which serves as a transcriptional regulator, indicating that PCP1 activates a silent endogenous sucrose uptake system. The other suppressor clones encode either putative transcriptional regulators, protein kinases or enzymes involved in thiamine biosynthesis, ferredoxin reduction or glutamyl tRNA reduction and suppress the phenotype by unknown mechanisms.
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  • 76
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    Molecular genetics and genomics 248 (1995), S. 59-68 
    ISSN: 1617-4623
    Keywords: Yeast ; DNA repair ; SRS2 gene regulation ; Protein fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The expression of theSRS2 gene, which encodes a DNA helicase involved in DNA repair inSaccharomyces cerevisiae, was studied using anSRS2-lacZ fusion integrated at the chromosomalSRS2 locus. It is shown here that this gene is expressed at a low level and is tightly regulated. It is cell-cycle regulated, with induction probably being coordinated with that of the DNA-synthesis genes, which are transcribed at the G1-S boundary. It is also induced by DNA-damaging agents, but only during the G2 phase of the cell cycle; this distinguishes it from a number of other repair genes, which are inducible throughout the cycle. During meiosis, the expression ofSRS2 rises at a time nearly coincident with commitment to recombination. Sincesrs2 null mutants are radiation sensitive essentially when treated in G1, the mitotic regulation pattern described here leads us to postulate that either secondary regulatory events limit Srs2 activity to G1 cells or Srs2 functions in a repair mechanism associated with replication.
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  • 77
    ISSN: 1617-4623
    Keywords: Yeast ; Aspergillus ; CCAAT ; Acetamidase Carbon regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The upstream regulatory region of the amdS gene of Aspergillus nidulans contains a CCAAT sequence known to be important in setting both basal and derepressed levels of expression. We have investigated whether the CCAAT-binding HAP2/3/4 complex of the yeast Saccharomyces cerevisiae can recognise this sequence in an amdS context. Sequences from the 5′ region of amdS were cloned in front of the CYCI-lacZ fusion gene bearing a minimal promoter and transformed into wild-type and hap2 strains of yeast. This study has indicated that amdS sequences are capable of promoting regulated expression of the fusion gene in response to carbon limitation. The yeast HAP2/3/4 complex can recognise the amdS CCAAT sequence and activate expression from this sequence. In addition, the results indicate that other yeast proteins can also regulate expression from the A. nidulans amdS 5′ sequences under carbon-limiting conditions.
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  • 78
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    Molecular genetics and genomics 247 (1995), S. 137-147 
    ISSN: 1617-4623
    Keywords: Calmodulin ; Gain-of function mutations ; Yeast ; Cell growth ; Target recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A human epithelial cell-specific transcript (NB-1) encodes a calmodulin-like protein (hCLP), which is identical in length and 85% identical in amino acid sequence to authentic human calmodulin (hCaM). Although hCaM shares only 60% amino acid sequence identity with yeast calmodulin (CMD1 gene product), hCaM was able to substitute functionally for Cmd1 in yeast cells. In contrast, hCLP was unable to support either spore germination or vegetative growth in Cmd1-deficient yeast cells, even when stably expressed at a level at least an order of magnitude above that of hCaM. Thus, hCLP provides an indicator protein for discerning those residues that are critical for calmodulin function in vivo. In addition to 20 conservative amino acid replacements, hCLP differs from hCaM (and other vertebrate calmodulins that are able to complement acmd1 null mutation) by only three nonconservative substitutions. Site-directed mutagenesis was used to convert these three positions back to residues more typical of those found in authentic calmodulins and to prepare all possible combinations of these three mutations, specifically: three single mutants (R58V, R112N, and A128E), three double mutants (R58V A128E, R112N A128E, and R58V R112N), and the triple mutant (R58V R112N A128E). The triple mutant and one of the double mutants (R58V A128E) were able to restore an apparently normal growth rate to acmd1Δ strain, indicating that the altered hCLPs have acquired the ability to behave as functional calmodulins in yeast. The other two double mutants were able to support growth of Cmd1-deficient cells only weakly, but cells expressing the R112N A128E mutant grew noticeably better than those expressing the R58V R112N mutant. Remarkably, one single mutant (A128E), but not the other two single mutants, was also reproducibly able to support weak growth of acmd1Δ strain. The properties of these gain-of-function, or neomorphic, mutations implicate E128, and to a lesser extent V58, as residues critical for calmodulin action in vivo. Molecular modeling of these positions within the structure of a Ca2+-calmodulin · peptide complex indicates that E128 projects directly into the central cavity occupied by the bound peptide. Thus, E128 may contribute a contact that is vital for the interaction of Cmd1 with one or more of the targets that are essential for yeast cell growth.
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  • 79
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    Molecular genetics and genomics 207 (1987), S. 273-279 
    ISSN: 1617-4623
    Keywords: Yeast ; Galactose metabolism ; Gene fusion ; Upstream activating sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have suggested previously from Northern blot analysis that transcription of the negative regulatory gene GAL80 was controlled positively by another regulatory gene GALA, and negatively by GAL80 itself, in similar way to GAL1, GAL7 and GAL10 genes encoding galactosemetabolizing enzymes in Saccharomyces cerevisiae. To study further the controlled expression of GAL80, we have exploited the gene fusion technique. We constructed gene fusions consisting of 5′ fragments of GAL80 and a 5′ truncated lacZ of Escherichia coli, and introduced the GAL80‘-’lacZ fusions into wild-type yeast or various GALA or GAL80 mutants using multiple-copy or single-copy plasmid vectors. We then studied β-galactosidase activity in the resultant transformants under uninduced, induced or glucose-repressed conditions. Expression of the GAL80‘-’lacZ fusions was clearly under the control of Gal4/Gal80. Next we constructed GAL7‘-’lacZ fusions, whose upstream activating sequence (UAS) from GAL7 was replaced with a GAL80 fragment containing a UAS-like sequence located in the 5′ flanking region of GAL80. Synthesis of β-galactosidase directed by the hybrid genes was inducible by galactose exactly like the original GAL7‘-’lacZ fusion with a UAS from GAL7. Finally we constructed a GAL7-GAL80 hybrid gene, in which the entire 5′ flanking region was derived from GAL7. When the chromosomal GAL80 gene in wild-type yeast was replaced with the hybrid gene, the uninduced level, but not the induced level, of the GAL10-encoded enzyme (uridine diphosphoglucose-4-epimerase) was significantly increased.
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  • 80
    ISSN: 1617-4623
    Keywords: Yeast ; URA2 ; Glutamine amidotransferase ; Multifunctional protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Yeast URA2 encodes a multifunctional carbamoyl phosphate synthetase-aspartate transcarbamylase of 220,000 molecular weight. We determined the nucleotide sequence of the 5′ proximal part of the gene which is responsible for the glutamine amide transfer function of the carbamoyl phosphate synthetase activity. Alignment of the enzyme sequence derived from URA2 with sequences from Escherichia coli carA carB and yeast arginine-specific CPA1 CPA2 indicates that monofunctional and bifunctional carbamoyl phosphate synthetases are probably homologous. The URA2-derived enzyme organization is NH2-carbamoyl phosphate synthetase-aspartate transcarbamylase-CO2H.
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  • 81
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    Molecular genetics and genomics 209 (1987), S. 142-148 
    ISSN: 1617-4623
    Keywords: Yeast ; rad mutants ; DNA alkylations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The radiation-sensitive rad mutants of the yeast Saccharomyces cerevisiae exhibit a complex pattern of sensitivity to simple monofunctional alkylating agents. The RAD1, RAD2, RAD4 and RAD14 genes of the RAD3 epistasis group are implicated in the repair of ethylations to DNA. The RAD3, RAD10 and RAD16 genes of this group are not involved. The RAD4 and RAD14 genes have a particular role in repair following exposure to those ethylating agents that preferentially alkylate oxygen, but not to those that preferentially ethylate nitrogen. The RAD1 and RAD2 genes are involved in the repair of damage induced by all the ethylating agents used except EMS. The mutants in this group that are sensitive to ENU were not sensitive to MNU, suggesting that nucleotide excision operates on ethylations but not on methylations. In the RAD6 group, the RAD6 and RAD18 genes are involved in DNA repair after exposure to all the alkylating agents tested, whereas RAD8 appears to have a role in the repair of O-alkylations but not N-alkylations. RAD9 operates in the repair of methylations and ethylations, but does not influence events after exposure to EMS. In the RAD52 group, the mutants tested were sensitive to ENU and DES. Thus some members of all three epistasis groups are involved in the repair of alkylations to DNA.
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  • 82
    ISSN: 1617-4623
    Keywords: Yeast ; DNA repair ; RAD genes ; UV radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutations in the RAD3 gene of Saccharomyces cerevisiae were generated by integration of a mutagenized incomplete copy of the cloned gene into wild-type cells. Integrants were mass screened for colonies with abnormal growth characteristics at 37°C. A single temperature-sensitive mutant (rad3ts-1) was isolated and was shown to result from a missense mutation at codon 73 of the RAD3 gene. When shifted from 30° C to 37° C the strain undergoes only 2–4 cell doublings. This phenotype can be rescued by plasmids in which the essential function of the cloned RAD3 gene is intact, but not plasmids in which this function is inactivated. The mutant strain is weakly sensitive to ultraviolet (UV) radiation at restrictive temperatures. Measurement of RNA, DNA and protein synthesis at various times after shifting to restrictive temperatures does not show preferential inactivation of any one of these parameters and the temperature-sensitive mutation does not cause arrest at any specific phase of the cell cycle. The rad3ts-1 strain was transformed with multicopy plasmids from a normal yeast genomic library and two plasmids that partially suppress the temperature-sensitive phenotype were isolated. These suppressor genes (designated SRE1 and SRE2) are distinct from RAD3 and do not suppress the phenotype of several other temperature-sensitive mutants tested. Mutant strains carrying disruptions of the SRE1 gene are viable and are not sensitive to UV or γ radiation.
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  • 83
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    Molecular genetics and genomics 210 (1987), S. 16-22 
    ISSN: 1617-4623
    Keywords: Centromere ; Repair ; UV ; Yeast ; Pyrimidine dimers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The centromere is the region within a chromosome that is required for proper segregation during mitosis and meiosis. Lesions in this sequence represent a unique type of damage, as loss of function could result in catastrophic loss of the genetic material of an entire chromosome. We have measured the induction by ultraviolet (UV) light of pyrimidine dimers in a 2550-bp restriction fragment that includes the centromere region of chromosome III in Saccharomyces cerevisiae. Yeast cells were exposed to ultraviolet light, cellular DNA was gently extracted, and subsequently treated with a UV-specific endonuclease to cleave all pyrimidine dimers. The sites of UV-specific nuclease scission within the centromere were determined by separating the DNA according to molecular weight, transferring the fragments to nitrocellulose, and hybridizing to a radiolabeled 624-bp fragment homologous to the centromere DNA from chromosome III. Several hotspots were identified in chromatin DNA from cells, as well as in irradiated deproteinized DNA. Double strand damage due to closely opposed pyrimidine dimers was also observed. At biological doses (35% survival) there are approximately 0.1 to 0.2 pyrimidine dimers per centromere. These dimers are efficiently repaired in the centromere and surrounding region.
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  • 84
    ISSN: 1617-4623
    Keywords: Microbial protease ; Proenzyme ; Secretion ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The aspartic protease gene of a zygomycete fungus Mucor pusillus was expressed in Saccharomyces cerevisiae under the control of the yeast GAL7 promoter. A putative preproenzyme with an NH2-terminal extension of 66 amino acids directed by the gene was processed in yeast cells and the mature enzyme, whose NH2-terminus was identical to that of the Mucor enzyme, was efficiently secreted into the medium at a concentration exceeding 150 mg/l. The enzyme secreted from the recombinant yeast was more glycosylated than the native Mucor enzyme but its enzymatic properties were almost identical with those of the native enzyme, which has been used as a milk coagulant in cheese manufacture.
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  • 85
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    Molecular genetics and genomics 210 (1987), S. 581-583 
    ISSN: 1617-4623
    Keywords: Allosuppressor ; Saccharomyces cerevisiae ; Yeast ; Translational fidelity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The fidelity of translation in the yeast Saccharomyces cerevisiae is controlled by a number of gene products. We have begun a molecular analysis of such genes and here describe the cloning and analysis of one of these genes, SAL3. Mutations at this locus, and at least four other unlinked loci (designated SAL1-SAL5), increase the efficiency of the tRNA ochre suppressor SUQ5, and are thus termed allosuppressors. We have cloned the SAL3 gene from a yeast genomic library by complementation of a sal3 mutation. Integration of the cloned sequence into the yeast chromosome was used to confirm that the SAL3 gene had been cloned. SAL3 gene is present in a single copy in the yeast genome, is transcribed into a 2.3-kb polyadenylated mRNA and encodes a protein of Mr 80 000. The size of the SAL3 gene product strongly suggests that it is not a ribosomal protein.
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  • 86
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    Journal of industrial microbiology and biotechnology 14 (1995), S. 240-246 
    ISSN: 1476-5535
    Keywords: Yeast ; Copper ; Silver ; Ion selective electrodes ; Metal complexation ; Metal uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Three strains ofSaccharomyces cerevisiae and one strain of aCandida sp. obtained from different industrial sources were screened for uptake of silver and copper. Considerable differences in metal uptake capacities were found between the different strains ofS. cerevisiae and betweenS. cerevisiae and theCandida sp. used. Copper uptake capacities ranged from 0.05 mmol g−1 dry wt to 0.184 mmol g−1 dry wt while values of 0.034 mmol Ag g−1 dry wt and 0.193 mmol Ag g−1 dry wt biomass were observed. Use of ion-selective electrodes (ISEs) enabled the detection of copper complexing agents (possibly proteins and carbohydrates) released by yeasts into the surrounding medium. In contrast, these compounds had no silver complexation abilities. Langmuir and Scatchard transformations of metal adsorption isotherms suggested differences in the mechanisms involved in metal uptake by the various yeasts. The differences between strains ofS. cerevisiae were due possibly to differences in cell wal composition. Different methods of preparation of biomass (fresh, air, oven and freeze-dried) had little effect on metal uptake in comparison with fresh biomass. Storage of fresh waste biomass at 4°C for 20 days had no effect on metal biosorption capacities. It was also observed that individual batches of waste biomass produced from different fermentation runs had consistent metal uptake capacities. The implications of the above results on the use of waste yeast biomass for treatment of metal-containing effluents are discussed.
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  • 87
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    Journal of industrial microbiology and biotechnology 14 (1995), S. 502-507 
    ISSN: 1476-5535
    Keywords: Phaffia rhodozyma ; Astaxanthin ; Carotenoids ; Yeast ; Singlet oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The only known habitat of the astaxanthin-containingPhaffia rhodozyma is in slime fluxes of deciduous trees at high altitudes. In this habitat, the function of carotenoids inP. rhodozyma is probably to provide protection against photogenerated antifungal substances in the tree flux such as singlet oxygen (1O2). To investigate the role of carotenoids inP. rhodozyma, genetic selections were employed to determine if carotenogenic yeast strains ofP. rhodozyma have enhanced ability to quench1O2. Singlet oxygen was generated in liquid culture by the interaction of visible light (λ-550 nm) with the photosensitizer rose bengal or by the activation of α-terthienyl with ultraviolet light (λ=366 nm). In each case the treatments selected for growth of pigmented strains ofP. rhodozyma. Albino (carotenoid-less) or yellow (β-carotene producing) strains grew less well in media containing1O2. Addition of the1O2 quencher sodium azide to the medium with α-terthienyl allowed growth of non-pigmented strains. Since the ecological niche ofP. rhodozyma is highly specific, we investigated whether extracts of birch trees (Betula), the original source ofP. rhodozyma, contained a compound that would select for pigmented populations of the yeast. WhenP. rhodozyma strains were exposed to ethyl acetate extracts ofBetula papyrifera excited with 366 nm ultraviolet light, only pigmented cells were able to grow. These results suggest that carotenogenesis developed inP. rhodozyma in response to the presence of photoactivatable antifungal compounds produced by the host tree.
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  • 88
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    Journal of industrial microbiology and biotechnology 2 (1987), S. 79-85 
    ISSN: 1476-5535
    Keywords: Yeast ; Bacteria ; High cell density ; Oxygen transfer ; Heat transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary High-productivity continuous fermentation processes have been developed for the production of important industrial microorganisms in specially designed fermentors.Saccharomyces cerevisiae, Pichia pastoris, Kluyveromyces fragilis, andCandida utilis yeasts have been grown in bench-scale fermentors at cell densities of over 120 g/l, whileEscherichia coli, Bacillus megaterium, Methylomonas sp. andPseudomonas putida bacteria have been cultivated to cell densities of more than 110 g/l. Productivities (g cells per 1 per h) greater than 25 have been achieved in both bench-scale and 1500-liter fermentors with yeasts, and values as high as 55 have been achieved with bacteria in the bench-scale fermentor. The microorganisms were grown on defined media using ammonia for pH control and as nitrogen source. The fermentor, capable of high oxygen and heat transfer rates, was operated at constant volume with continuous feed and product discharge. The high-productivity process reduces fermentor size, media sterilization requirements, and may under some circumstances eliminate waste and recycle streams. It can also be applied to a variety of biological products.
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  • 89
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    Journal of industrial microbiology and biotechnology 2 (1987), S. 167-174 
    ISSN: 1476-5535
    Keywords: Selection ; Yeast ; Fitness distribution ; Mutation ; Saccharomyces cerevisiae ; Computer simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The fitness distribution of new mutations inSaccharomyces cerevisiae strain Montrachet was determined for cells on agar irradiated for four periods of time with ultraviolet light. The fitness distributions were obtained by converting a large number of colony diameters into relative fitnesses. The distributions were then used to perform a computer simulation with the purpose of predicting the potential of a stock culture to increase in general fitness through selection, given a frequency and magnitude of mutations.
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  • 90
    ISSN: 1476-5535
    Keywords: Yeast ; Oleaginous ; Rhodotorula glutinis ; Lipid ; Fat ; Molasses ; Fed batch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Rhodotorula glutinis is known to produce fat when cultivated under nitrogen-limiting conditions. Economically, molasses is an ideal substrate, however, due to the presence of nitrogen in molasses, the lipid yield obtained is much lower than that obtained from glucose or sucrose. Higher yields were obtained using molasses in a fed batch fermentation supplemented with glucose or sucrose during the lipid accumulation phase. The fatty acids profile of the lipids thus produced, using a very simple and economical medium, was similar to that obtained from glucose and sucrose.
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  • 91
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    Journal of industrial microbiology and biotechnology 14 (1995), S. 355-364 
    ISSN: 1476-5535
    Keywords: Transformation ; Fungi ; Yeast ; Genetics ; Biotechnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The genetic investigation of fungi has been extended substantially by DNA-mediated transformation, providing a supplement to more conventional genetic approaches based upon sexual and parasexual processes. Initial transformation studies with the yeastSaccharomyces cerevisiae provided the model for transformation systems in other fungi with regard to methodology, vector construction and selection strategies. There are, however, certain differences betweenS. cerevisiae and filamentous fungi with regard to type of genomic insertion and the availability of shuttle vectors. Single-site linked insertions are common in yeast due to the high level of homology required for recombination between vectored and genomic sequences, whereas mycelial fungi often show a high frequency of heterologous and unlinked insertions, often in the form of random and multiple-site integrations. While extrachromosomally-maintained or replicative vectors are readily available for use with yeasts, such vectors have been difficult to construct for use with filamentous fungi. The development of vectors for replicative transformation with these fungi awaits further study. It is proposed that replicative vectors may be inherently less efficient for use with mycelial fungi relative to yeasts, since the mycelium, as an extended and semicontinuous network of cells, may delimit an adequate diffusion of the vector carrying the selectable gene, thus leading to a high frequency of abortive or unstable transformants.
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  • 92
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    Journal of industrial microbiology and biotechnology 14 (1995), S. 389-395 
    ISSN: 1476-5535
    Keywords: Astaxanthin ; Yeast ; Pigment ; Corn wet-milling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Natural isolates of the carotenoid-producing yeastPhaffia rhodozyma were analyzed for their ability to grow and to produce carotenoids in culture media composed exclusively of co-products of corn wet-milling for fuel ethanol production. FiveP. rhodozyma strains were tested for biomass produced (dry weight) and carotenoid yield. Six co-products were examined, ranging in cost from approximately $0.02 per kg to $0.11 per kg, all less expensive than conventional or agricultural growth substrates previously tested. The three co-products allowing the greatest accumulation of biomass and carotenoids byP. rhodozyma were thin stillage (TS), corn condensed distiller's solubles (CCDS) and corn gluten feed (CGF). Of the medium compositions tested, 10–15% CGF, 70% TS and 6–8% CCDS generally allowed maximum carotenoid production. Cultures grown in these three media produced up to 65%. 148% and 104% of the carotenoid yield per ml of yeast extract/malt extract (YM) cultures, respectively. Under the conditions tested, this was at an approximate medium cost of $0.67 per g carotenoids for CCDS and $0.73 per g for CGF as compared to $385.00 per g for YM. These results indicate that certain co-products of corn wet-milling can serve, at the appropriate concentration, as efficient, economical substrates for growth and carotenoid production byPhaffia rhodozyma.
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  • 93
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    Methods in cell science 17 (1995), S. 283-294 
    ISSN: 1573-0603
    Keywords: Yeast ; Vacuole ; Membrane fusion ; Organelle inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Homotypic (self) vacuole fusion is the last discernible step in vacuole inheritance ofSaccharomyces cerevisiae and was recently successfully reconstituted in vitro using purified vacuoles, cytosol, ATP, moderate salt concentrations, and a physiological temperature. The following protocol describes a rapid, reliable, and easy technique to quantitate homotypic vacuole fusion in vitro. Frequency of fusion is determined by quantifying alkaline phosphatase activity after fusion has taken place. This method has been successfully used to analyze pharmacological reagents which interfere with certain subreactions and to identify distinct proteins which play key roles in the fusion events.
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