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  • 1
    ISSN: 1432-1432
    Keywords: Squalus acanthias ; Carbamoyl-phosphate synthetase ; Promoter ; Rana catesbeiana ; TATA box ; TACAAA ; C/EBP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carbamoyl-phosphate synthetase III (CPSase III) ofSqualus acanthias (spiny dogfish) is a nuclear-encoded mitochondrial enzyme that catalyzes glutamine-dependent formation of carbamoyl phosphate for urea synthesis. In this paper we report the results of cloning a 10-kb segment of genomic DNA which includes the region flanking the 5′ end of the spiny dogfish CPSase III gene. A total of 1,295 base pairs of sequence straddling the start codon was obtained. Primer extension experiments revealed that the transcription start site is the G located 114 residues upstream of the translation start codon ATG. The first exon has 240 base pairs, including the 5′ untranslated region, the coding sequence for the signal peptide (38 amino acids), and the four N-terminal amino acids of the mature enzyme. The boundary of the first exon and the first intron of the CPSase III gene is concordant with that of rat and frog (Rana catesbeiana) CPSase I, which have been suggested to have evolved from CPSase III. The putative TATA box sequence, TACAAA, is located at position −31 with an uncommonly found C at the third position. Two C/EBP binding site sequences, ATTCTGCAAG (−405 to −397) and GTGCAGTAAG (−168 to −160), were identified in the promoter region, which suggests that spiny dogfish CPSase III might be subjected to transactivation of transcription by C/EBP-related proteins, as has been reported for rat CPSase I. The preparation and binding of a recombinant RcC/EBP-1 protein (theR. catesbeiana homolog of the mammalian C/EBPα) to the two spiny dogfish C/EBP binding sequences are described. Two putative heatshock binding elements were also identified in the promoter region.
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  • 2
    ISSN: 1573-5028
    Keywords: heat shock ; heat shock cDNAs ; maize ; small heat shock proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Heat-shocked maize seedlings (cv. Oh43) synthesize a characteristic set of heat-shock proteins (hsps) which include an 18 kDa family containing at least six major isoelectric variants. A cDNA library was constructed from poly(A)+ RNAs isolated from the radicles of heat-shocked maize seedlings and screened with a DNA fragment from the theoretical open reading frame of a putative Black Mexican Sweet maize hsp 18 genomic clone. Two clones, cMHSP18-3 and cMHSP18-9, were isolated, and the RNA transcripts generated from them were translated into proteins which immunoreact with antibodies directed against the maize 18 kDa hsps and exhibit the same electrophoretic characteristics as two different members of the 18 kDa hsp family. Nucleotide sequence analyses of the cDNAs in these clones reveal that their 5′ and 3′ untranslated regions exhibit 33–34% identity and that their protein encoding regions share 93% identity. The deduced amino acid sequences of these clones show 90% identity, and the apparent molecular masses and isoelectric points of these proteins agree with those established for two different 18 kDa hsps, numbered 3 and 6. This report substantiates that at least two of the 18 kDa hsps in maize are products of different but related genes. Moreover, it establishes that transcripts for these proteins accumulate during heat shock and that both their nucleotide and deduced amino acid sequences share extensive similarities with the class VI small hsps in soybean and with transcripts expressed during meiosis in Lilium.
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  • 3
    ISSN: 1573-5028
    Keywords: carotenoid biosynthesis ; endosperm ; gene ; maize ; phytoene desaturase ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To study regulation of the plastid-localized maize carotenoid biosynthetic pathway, a cDNA encoding phytoene desaturase (PDS) was isolated and characterized. The DNA sequence of the maize Pds cDNA was determined and compared with available dicot Pds genes. The deduced PDS protein, estimated at 64.1 kDa (unprocessed), had a dinucleotide binding domain and conserved regions characteristic of other carotene desaturases. Alignment of available PDS sequences from distantly related organisms suggests that Pds has potential as a phylogenetic tool. By use of heterologous complementation in Escherichia coli, maize PDS was shown to catalyze two desaturation steps converting phytoene to ζ-carotene. RFLP (restriction fragment length polymorphism) mapping was used to place Pds on chromosome 1S near viviparous5 (vp5), and RT-PCR (reverse-transcriptase polymerase chain reaction) analysis indicated reduced Pds transcript in vp5 mutant relative to normal endosperm. Other phytoene-accumulating mutant endosperms, vp2 and white3 (w3), showed no difference in Pds transcript accumulation as compared with normal endosperm counterparts. RT-PCR analysis of Pds transcript accumulation in developing endosperm showed Pds was constitutively expressed. Therefore, endosperm carotenogenesis is not regulated by increasing the level of Pds transcripts.
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  • 4
    ISSN: 0192-253X
    Keywords: C/EBP ; thyroid hormone ; metamorphosis ; gene expression ; Rana cafesbeiana ; bZlP proteins ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Tissue-specific changes in gene expression occur in the liver of Rana cafesbeiana tadpoles undergoing metamorphosis. Many of these changes can be induced precociously by administration of thyroid hormone (TH) to a tadpole or to cultured tadpole liver. While the precise molecular means by which TH exerts a tissue-specific response is unknown, recent studies suggest that the expression of genes which are liver-specific and characteristic of the adult liver phenotype may rely on TH-induction of tissue-specific transcription factors, as well as the thyroid hormone receptor proteins. Guided by this notion, we screened our Rana catesbeiana liver cDNA library and isolated clones, RcC/EBP-1 and -2, encoding Rana homologues of a mammalian transcription factor, C/EBP (CCAAT/enhancer core binding protein), implicated in the expression of liver-specific genes and terminal differentiation of hepatocytes. Gel mobility shift assays demonstrate that the proteins synthesized from these cDNAs bind specifically to the consensus binding site for C/EBP-related proteins. Characterization of the amino acid sequence in the bZlP DNA-binding domains of these proteins suggests that RcC/EBP-1 and -2 encode Rana homologues of C/EBPα and δ, respectively. Hybridization analyses demonstrate that the amount of RcC/EBP-2 mRNAs in tadpole liver remains constant throughout metamorphosis, whereas RcC/EBP-1 mRNAs are up-regulated during both spontaneous and TH-induced metamorphosis. The TH-induced up-regulation of RcC/ EBP-1 mRNAs precedes the up-regulation of liver-specific urea cycle enzyme mRNAs by 6 to 12 hours. These results, coupled with in situ hybridization studies, suggest that RcC/EBP-1 mRNAs encode a transcription factor which may play an early role(s) in the terminal differentiation and/or reprogramming of gene expression in this tadpole's liver cells during both spontaneous and TH-induced metamorphosis. ©1994 WiIey-Liss, Inc.
    Additional Material: 8 Ill.
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  • 5
    ISSN: 0192-253X
    Keywords: Heat shock protein ; maize ; mi-crosporogenesis ; gametogenesis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The small (18-kDa) heat shock proteins (hsps) of maize are encoded by a complex multigene family. In a previous report, we described the genetic information from cDNAs encoding two different members of the family. In this communication, we report the isolation and characterization of cDNA and genomic clones encoding information for a third member of this hsp family (c/gMHSP18-1). DNA fragments containing nucleotide sequences common to, or specific for, each of these characterized 18-kDa genes were prepared and used as probes to assess the expression of these genes during microsporogenesis and development of the gametophyte in an inbred line of maize (Oh43). Our results demonstrate (1) that mRNA transcripts encoding the 18-kDa hsps are expressed and/or accumulate during microsporogenesis, and (2) that genes encoding two of the characterized 18-kDa hsps are expressed and/or accumulate independently, in a stage-specific manner during microsporogenesis. These observations imply that the stage-specific expression of particular 18-kDa hsp genes results from gene-specific regulation during microsporogenesis and gametophyte development rather than from an overall activation of the heat shock or stress response. © 1993Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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