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  • 1
    Electronic Resource
    Electronic Resource
    Changes in heat shock protein synthesis and heat sensitivity during mouse thymocyte development (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 14 (1993), S. 148-158 
    Details
    ISSN: 0192-253X
    Keywords: Apoptosis ; DNA fragmentation ; T-cell development ; heat shock proteins ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Heat shock protein synthesis was examined in mouse thymocytes at three stages of development: early embryonic thymocytes, which are CD4-CD8-, adult thymocytes, which are primarily CD4+CD8+, and mature spleen T cells, which are CD4+CD8- or CD4-CD8+. After either a 41°C or 42°C heat shock, the synthesis of the maior heat-inducible protein (hsp68) was elevated during the first hour of recovery but then decreased abruptly in thymocytes from adult mice. In contrast, the synthesis of hsp68 continued for up to 4 h after heating embryonic mouse thymocytes or mature spleen T cells. The more rapid termination ofthe heat shock response in the adult thymocytes was not the result of eitherless heat damage or more rapid repair since the recovery of general protein synthesis was more severely delayed in these cells. As well, the double positive CD4+CD8+ cells were more sensitive to hyperthermia than either the double negative CD4-CD8- or single positive CD4+CD8- or CD4-CD8+ cells. Exposure of fetal thymus organ cultures to elevated temperature revealed that the double negative thymocytes were able to survive and differentiate normally following a heat shock treatment that was lethal for the double positive thymocytes. Exposure of thymocytes from adult mice to elevated temperatures induced apoptotic cell death. This was evident by the cleavage of DNA into oligonucleosome-sized fragments. Quantitation of the extent of DNA fragmentation and the number of apoptotic cells by flow cytometry demonstrated that the extent of apoptotic cell death was related to the severity of the heat stress. Double positive (CD4+CD8+) thymocytes are selected on the basis of their T-cell antigen receptor (TCR). Most of these cells are negatively selected and die within the thymus by an active process of cell deletion known as apoptosis. Restricting hsp synthesis in response to stress might be essential during developmental processes in which cell maturation is likely to result in death rather than functional differentiation. © 1993Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020140209
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  • 2
    Electronic Resource
    Electronic Resource
    A new glucose-repressible gene identified from the analysis of chromatin structure in deletion mutants of yeast SUC2 locus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 7 (1991), S. 379-389 
    Details
    ISSN: 0749-503X
    Keywords: Chromatin ; SUC2 ; Glucose repression ; 3-Oxoacyl-CoA thiolase gene ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have previously shown that some changes occur in the chromatin structure of the 3′ flank of the yeast SUC2 gene in going from a repressed to an active state. In an attempt to find out the causes of these changes, we have carried out experiments in which mutant copies of SUC2 locus lacking either 5′ or 3′ flanks have been analysed for their transcriptional activity and chromatin structure. These experiments allowed us to discard any relationship between SUC2 transcription and chromatin changes within its 3′ flank. Sequencing of this flank and mRNA analysis, however, resulted in the location of a putative peroxisomal 3-oxoacyl-CoA thiolase gene (POT1), which is repressible by glucose. The disruption of the gene produced a yeast strain unable to use oleic acid as a carbon source. This is the first time that chromatin structure analysis has permitted the identification of new gene.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320070408
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  • 3
    Electronic Resource
    Electronic Resource
    Chromatin structure of the yeast FBP1 gene: Transcription-dependent changes in the regulatory and coding regions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 1229-1240 
    Details
    ISSN: 0749-503X
    Keywords: Fructose-1,6-bisphosphate ; hypersensitive sites ; nucleosome positioning ; psoralen crosslinking ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the chromatin structure of the Saccharomyces cerevisiae FBP1 gene, which codes for fructose-1,6-bisphosphatase. A strong, constitutive, DNase I, micrococcal nuclease and S1 nuclease hypersensitive site is present close to the 3′ end of the coding region. In the repressed state, positioned nucleosomes exist around this site, and subtle changes occur in this nucleosomal organization upon derepression. A DNase I hypersensitive region is located within the promoter between positions -540 and -400 and it extends towards the gene in the derepressed state, leading to an alteration of nucleosomal positioning. Psoralen crosslinking of chromatin, which is used for the first time to study the mobility of restriction fragments from an RNA polymerase II gene, revealed that part of the promoter is nucleosome-free, in accordance with the results of DNase I digestion. A model is presented that, based on the chromatin structure, puts forward the hypothesis that the promoter UAS is located between - 540 and - 340. Finally, psoralen crosslinking, as well as digestions with micrococcal nuclease or restriction endonucleases suggests that most if not all of the copies of the active FBP1 gene are covered by nucleosomes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320091110
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  • 4
    Electronic Resource
    Electronic Resource
    Reduced efficiency in the glycosylation of the first sequon of Saccharomyces cerevisiae exoglucanase leads to the synthesis and secretion of a new glycoform of the molecule (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 9 (1993), S. 221-234 
    Details
    ISSN: 0749-503X
    Keywords: Exoglucanase (β)-glucosidase ; secretion ; glycosylation ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In addition to exoglucanases (EXGs) I and II, old cultures of Saccharomyces cerevisiae secreted into the culture medium a new immunologically-related material that exhibited exoglucanase activity. The new exoglucanase (EXGII1/2) was purified from stationary-phase cultures. It turned out to be a glycoprotein whose protein portion was identical to that of the other two isoenzymes in terms of ionic properties, size, amino acid composition and NH2-terminal sequence (25 residues). Disruption of the structural gene encoding EXGs I and II resulted in a strain unable to secrete all three isoenzymes. EXGII1/2 was indistinguishable in terms of molecular weight from the single intermediate detected during the deglycosylation (mediated by endo H) of EXGII by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Thus, the new isoenzyme contains only one of the two slightly elongated mannan inner cores present in enzyme II. Two intermediates were, however, detected when the deglycosylation of EXGII was monitored by ion-exchange chromatography (high-pressure liquid chromatography). Site-directed mutagenesis indicated that the major intermediate, which eluted at about the same position as enzyme II1/2, corresponded to protein molecules carrying the oligosaccharide attached to the Asn of the second sequon, whereas the minor one carried the oligosaccharide in the first potential glycosylation site. Several lines of evidence indicate that EXGII1/2 is a biosynthetic product resulting from an imbalance between the rate of protein synthesis and the glycosylation capabilities of the glycosylation machinery.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320090303
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