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Query: UNIPROT:P06889 (Mol)
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We found that the introduction into a yeast cell of a high-copy-number plasmid containing the 5' end of the SPS2 gene, a sporulation-specific gene of Saccharomyces cerevisiae, led to a reduction in the efficiency of spore formation. The plasmid pAP290, which contains the sequence from -138 to +152 of the SPS2 gene, caused a fivefold reduction in spore formation; the presence of the plasmid had no effect on transcription of the chromosomal SPS2 gene. A plasmid containing only the sequence upstream of the TATA box of the SPS2 gene (-350 to -68) was unable to inhibit the completion of sporulation, whereas the downstream sequence, from -70 to +404, although unable by itself to inhibit sporulation, could do so when provided with an upstream fragment containing the CYC1 upstream activation sequence. Deletion of 22 base pairs from pAP290, which introduced a frameshift after codon 17 of the SPS2 gene and reduced the open reading frame to 26 amino acids, generated a plasmid (pAP290 delta Pst) which could no longer inhibit sporulation. The SPS2 inserts of pAP290 and pAP290 delta Pst were found to direct equivalent levels of sporulation-specific transcription. We conclude from these results that the presence of both the SPS2 promoter (or a substitute promoter) and the initial coding sequence of the SPS2 gene is required in the high-copy-number plasmid to generate the asporogenous phenotype. We speculate that the accumulation of a protein containing the amino-terminal portion of the SPS2 gene product, synthesized from the transcripts of the truncated plasmid-borne copies of the SPS2 gene, prevents ascus formation.
Mol Cell Biol 1987 Jul
PMID:Increased copy number of the 5' end of the SPS2 gene inhibits sporulation of Saccharomyces cerevisiae. 330 78

Saccharomyces cerevisiae has two homologous hexokinases, I and II; they are 78% identical at the amino acid level. Either enzyme allows yeast cells to ferment fructose. Mutant strains without any hexokinase can still grow on glucose by using a third enzyme, glucokinase. Hexokinase II has been implicated in the control of catabolite repression in yeasts. We constructed null mutations in both hexokinase genes, HXK1 and HXK2, and studied their effect on the fermentation of fructose and on catabolite repression of three different genes in yeasts: SUC2, CYC1, and GAL10. The results indicate that hxk1 or hxk2 single null mutants can ferment fructose but that hxk1 hxk2 double mutants cannot. The hxk2 single mutant, as well as the double mutant, failed to show catabolite repression in all three systems, while the hxk1 null mutation had little or no effect on catabolite repression.
Mol Cell Biol 1986 Nov
PMID:Effects of null mutations in the hexokinase genes of Saccharomyces cerevisiae on catabolite repression. 354 Jun 5

In Saccharomyces cerevisiae the anaerobic (oxygen-repressed) ANB1 gene and a group of aerobic (oxygen-induced) genes are coordinately regulated by the ROX1 gene. We report here that heme, known as an inducer of aerobic genes, also causes inhibition of ANB1 expression. Thus, in combination with the ROX1 gene product heme has an opposite effect on the expression of anaerobic and aerobic genes. Accumulation of ANB1 mRNA was sharply decreased in anaerobic cells grown in the presence of heme. This effect must operate at the level of transcription since heme also inhibited accumulation of CYC1 mRNA from an ANB1-CYC1 fusion. Heme precursors did not appear to function either as inhibitors or as activators. Oxygen itself also had no effect on transcription of ANB1. Repression by heme cannot be attributed to the respiratory competence conferred by heme since both ANB1 and the aerobic genes tr-1 and CYC1 were regulated normally in [rho 0] mutants. The results are consistent with a classical allosteric coeffector function for heme, although more indirect explanations are tenable. A role for the ROX1 gene product in transcriptional regulation can be inferred from the observation that there was no inhibition of ANB1 expression by heme in rox1 mutants. Judging from this epistasis the rox1 phenotype is not due to a defect in heme production; this would indicate that the ROX1 factor functions by mediating the effect of heme on transcription.
Mol Cell Biol 1986 Dec
PMID:Negative regulation of the Saccharomyces cerevisiae ANB1 gene by heme, as mediated by the ROX1 gene product. 354 Jun 7

Activation of the CYC1 upstream activation site (UAS2) and other Saccharomyces cerevisiae genes encoding respiratory functions requires the products of the regulatory loci HAP2 and HAP3. We present here the DNA sequence of the yeast HAP2 gene and an initial investigation into the function of its product. The DNA sequence indicated that HAP2 encoded a 265-amino-acid protein whose carboxyl third was highly basic. Also found in the sequence was a polyglutamine tract spanning residues 120 to 133. Several experiments described herein suggest that HAP2 encodes a direct activator of transcription. First, a bifunctional HAP2-beta-galactosidase fusion gene was localized to the yeast nucleus. Second, a lexA-HAP2 fusion gene was capable of activating transcription when bound to a lexA operator site. The additional requirement for the HAP3 product in activation is discussed.
Mol Cell Biol 1987 Feb
PMID:Sequence and nuclear localization of the Saccharomyces cerevisiae HAP2 protein, a transcriptional activator. 354 76

Expression of the Saccharomyces cerevisiae CYC1 gene produces mRNA with more than 20 different 5' ends. A derivative of the CYC1 gene (CYC1-157) was constructed with a deletion of a portion of the CYC1 5'-noncoding region, which includes the sites at which many of the CYC1 mRNAs 5' ends map. A 54-mer double-stranded oligonucleotide homologous with the deleted sequence of CYC1-157 and which included a low level of random base pair mismatches (an average of two mismatches per duplex) was used to construct mutants of the CYC1 gene and examine the role of the DNA sequence at and immediately adjacent to the mRNA 5' ends in specifying their locations. The effect of these mutations on the site selection of mRNA 5' ends was examined by primer extension. Results indicate that there is a strong preference for 5' ends which align with an A residue (T in the template DNA strand) preceded by a short tract of pyrimidine residues.
Mol Cell Biol 1985 Dec
PMID:Saccharomyces cerevisiae CYC1 mRNA 5'-end positioning: analysis by in vitro mutagenesis, using synthetic duplexes with random mismatch base pairs. 391 80

The cyc1-512 mutant of the yeast Saccharomyces cerevisiae contains a 38 base-pair deletion in the 3' non-coding region of the CYC1 gene, which encodes iso-1-cytochrome c. The deletion affects the CYC1 terminator, causing CYC1 mRNAs to be much longer and more unstable than normal. Previous genetic analysis of revertants of the cyc1-512 mutant indicated that the defect could be completely or partially restored by three classes of genetic events: chromosomal rearrangements; local genetic changes near the original cyc1-512 mutation; and suppressors at unlinked loci. We show that all the revertants with chromosomal rearrangements have breakpoints 3' to the CYC1 locus, resulting in the formation of CYC1 mRNA with new 3' non-coding regions and new 3' mRNA termini. One spontaneous cyc1-512 revertant has a 3' insertion that resembles a repetitive, transposable yeast sequence (Ty1); CYC1 transcripts end just within the bounds of this element. This study reveals that the different 3' non-coding sequences, which arose by chromosomal rearrangements, increase the stability of CYC1 mRNA and have varying effects upon the mRNA translational efficiency. Many of the cyc1-512 revertants contain only local genetic changes that create stronger terminators from the weak terminators observed in the cyc1-512 mutant. Several types of terminators in these revertants have been identified; some cause discrete termination over a relatively small region, while others cause heterogeneous termination over a 200 base-pair region. The DNA sequence changes for two cyc1-512 revertants occur in a region with homology to a consensus sequence for transcription termination in yeast that was proposed by Zaret & Sherman (1982). Two classes of extragenic suppressors of the cyc1-512 mutation have been identified. One class of the suppressors appears specifically to enhance termination at weak terminator sites, while the other class of suppressors appears to increase the stability of aberrantly long CYC1 mRNA. The results from this study support our previous suggestion (Zaret & Sherman, 1982) that, in contrast to the usual situation in higher eukaryotes, transcription termination and polyadenylation may be coupled processes in yeast.
J Mol Biol 1984 Jul 25
PMID:Mutationally altered 3' ends of yeast CYC1 mRNA affect transcript stability and translational efficiency. 608 37

A series of BAL31 deletions were constructed in vitro in the upstream region of the Saccharomyces cerevisiae CYC7 gene, encoding the iso-2-cytochrome c protein. These deletions identified two sites which play a role in governing the expression of this gene. A positive site, the deletion of which led to decreased CYC7 expression, lay ca. 240 base pairs 5' to the translational initiation codon (-240). A negative site, the deletion of which led to greatly increased levels of CYC7 expression, lay at ca. -300 bp. Deletion of both these sites resulted in low wild-type-like expression of the gene. Therefore, these two sites appear to act antagonistically to give the low wild-type levels of CYC7 expression. Within the region defined as containing the positive site, there is a sequence which bears some homology to the upstream activation sites in the regulated gene, CYC1, encoding the iso-1-cytochrome c protein.
Mol Cell Biol 1984 Oct
PMID:A positive regulatory site and a negative regulatory site control the expression of the Saccharomyces cerevisiae CYC7 gene. 609 36

We present the DNA sequence of a 914-base pair fragment from Saccharomyces cerevisiae that contains the GAL1-GAL10 divergent promoter, 140 base pairs of GAL10 coding sequence, and 87 base pairs of GAL1 coding sequence. From this fragment, we constructed four pairs of GAL1-lacZ and GAL10-lacZ fusions on various types of yeast plasmid vectors. On each type of vector, the fused genes were induced by galactose and repressed by glucose. The response of a GAL1-lacZ fusion to gal4 and gal80 regulatory mutations was similar to the response of intact chromosomal GAL1 and GAL10 genes. A set of deletions that removed various portions of the GAL10 regulatory sequences from a GAL10-CYC1-lacZ fusion was constructed in vitro. These deletions defined a relatively guanine-cytosine-rich region of 45 base pairs that contained sequences necessary for full-strength galactose induction and an adjacent guanine-cytosine rich 55 base pairs that contained sequences sufficient for weak induction.
Mol Cell Biol 1984 Oct
PMID:Use of lacZ fusions to delimit regulatory elements of the inducible divergent GAL1-GAL10 promoter in Saccharomyces cerevisiae. 639 Jan 81

A series of Saccharomyces cerevisiae plasmids and mutant derivatives containing fusions of the Escherichia coli galactokinase gene, galK, to the yeast iso-1-cytochrome c CYC1 transcription unit were used to study the sequences affecting the initiation of translation in S. cerevisiae. When the CYC1 AUG initiation codon preceded the galK AUG codon and coding sequence and either the two AUGs were out of frame with each other or a nonsense codon was located between them, the expression of the galK gene was extremely low. Deletion of the CYC1 AUG and its surrounding sequences resulted in a 100-fold increase in galK expression. This dependence of galK expression on the elimination of the CYC1 AUG codon was used to select mutations in that codon. Then the ability of these altered initiation codons to serve in translational initiation was determined by reconstruction of the CYC1 gene 3' to and in frame with them. Initiation was found to occur at the codons UUG and AUA, but not at the codons AAA and AUC. Furthermore the codon UUG, when preceded by an A three nucleotides upstream, served as a better initiation codon than when a U was substituted for the A. The efficiency of translation from these non-AUG codons was quantitated by using a CYC1/galK protein-coding fusion and measuring cellular galactokinase levels. Initiation at the UUG codon was 6.9% as efficient as initiation at the wild-type AUG codon when preceded by an A three nucleotides upstream, but was over 10-fold less efficient when a U was substituted for that A. Initiation at AUA was 0.5% as efficient as at AUG. The effects of the sequences preceding the initiation codon are discussed in light of these results.
Mol Cell Biol 1984 Jul
PMID:Saccharomyces cerevisiae ribosomes recognize non-AUG initiation codons. 639 Jan 86

CYC1 and sup4 are part of a tightly linked cluster of genes on chromosome X in the yeast Saccharomyces cerevisiae. Using as probes previously cloned fragments containing the CYC1 and sup4 genes, we have identified and cloned the deoxyribonucleic acid (DNA) present between these genes in one strain of yeast. We find that the CYC1 and sup4 genes are approximately 21 kilobases apart. In the same strain, the meiotic map distance is approximately 3.7 centimorgans, for a ratio of 5.6 kilobases per centimorgan in this interval. The physical mapping has allowed unambiguous determination of the orientation of CYC1 and sup4 relative to each other, the centromere, and a nearby transfer ribonucleic acid (tRNA(2Ser)) gene. The spontaneous mutation cyc1-1 inactivates the CYC1 gene as well as the neighboring loci OSM1 and RAD7. We have determined that a cyc1-1-bearing strain lacks approximately 13 kilobases of single-copy DNA from the CYC1-sup4 region, including all of the CYC1 coding information. There is a sequence homologous to the middle-repetitive element Ty1 at or near the breakpoint of the cyc1-1 deletion. We discuss the possibility that Ty elements play a role in the formation of such large, spontaneous deletions, which occur frequently in this region of chromosome X in certain yeast strains.
Mol Cell Biol 1981 Mar
PMID:Physical analysis of the CYC1-sup4 interval in Saccharomyces cerevisiae. 676 99


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