Identification of a new class of negative regulators affecting sporulation-specific gene expression in yeast.
We characterized two yeast loci, MDS3 and PMD1, that negatively regulate sporulation. Initiation of sporulation is mediated by the meiotic activator IME1, which relies on MCK1 for maximal expression. We isolated the MDS3-1 allele (encoding a truncated form of Mds3p) as a suppressor that restores IME1 expression in mck1 mutants. mds3 null mutations confer similar suppression phenotypes as MDS3-1, indicating that Mds3p is a negative regulator of sporulation and the MDS3-1 allele confers a dominant-negative phenotype. PMD1 is predicted to encode a protein sharing significant similarity with Mds3p. mds3 pmd1 double mutants are better suppressors of mck1 than is either single mutant, indicating that Mds3p and Pmd1p function synergistically. Northern blot analysis revealed that suppression is due to increased IME1 transcript accumulation. The roles of Mds3p and Pmd1p are not restricted to the MCK1 pathway because mds3 pmd1 mutations also suppress IME1 expression defects associated with MCK1-independent sporulation mutants. Furthermore, mds3 pmd1 mutants express significant levels of IME1 even in vegetative cells and this unscheduled expression results in premature sporulation. These phenotypes and interactions with RAS2-Val19 suggest that unscheduled derepression of IME1 is probably due to a defect in recognition of nutritional status.
Benni
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Waksman Institute of Microbiology, Rutgers, the State University of New Jersey, Piscataway 08854-8020, USA.
Neigeborn
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D050539:3-Isopropylmalate Dehydrogenase; D000429:Alcohol Oxidoreductases / Q000235:genetics; D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D005809:Genes, Regulator; D038362:Glycogen Synthase Kinase 3; D047908:Intracellular Signaling Peptides and Proteins; D008540:Meiosis; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011494:Protein Kinases / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid; D013172:Spores, Fungal
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C110020:MDS3 protein, S cerevisiae; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C051095:SSP1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C074274:pmd1 protein, S pombe; D000429:Alcohol Oxidoreductases; D050539:3-Isopropylmalate Dehydrogenase; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; C064979:IME2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D038362:Glycogen Synthase Kinase 3; C068124:MCK1 protein, S cerevisiae