Elements involved in S-adenosylmethionine-mediated regulation of the Saccharomyces cerevisiae MET25 gene.
In Saccharomyces cerevisiae, the MET25 gene encodes O-acetylhomoserine sulfhydrylase. Synthesis of this enzyme is repressed by the presence of S-adenosylmethionine (AdoMet) in the growth medium. We identified cis elements required for MET25 expression by analyzing small deletions in the MET25 promoter region. The results revealed a regulatory region, acting as an upstream activation site, that activated transcription of MET25 in the absence of methionine or AdoMet. We found that, for the most part, repression of MET25 expression was due to a lack of activation at this site, reinforced by an independent repression mechanism. The activation region contained a repeated dyad sequence that is also found in the promoter regions of other unlinked but coordinately regulated genes (MET3, MET2, and SAM2). We show that the presence of the two dyads is necessary for maximal gene expression. Moreover, we demonstrate that in addition to this transcriptional regulation, a posttranscriptional regulation, probably targeted at the 5' region of mRNA, is involved in MET25 expression.
Thomas
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Laboratoire d'Enzymologie du Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
Cherest
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Surdin-Kerjan
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D001483:Base Sequence; D019757:Carbon-Oxygen Lyases; D003547:Cysteine Synthase; D004252:DNA Mutational Analysis; D004262:DNA Restriction Enzymes; D005822:Genetic Vectors; D008190:Lyases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D011401:Promoter Regions, Genetic; D012323:RNA Processing, Post-Transcriptional; D012045:Regulatory Sequences, Nucleic Acid; D012436:S-Adenosylmethionine / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid
D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D012436:S-Adenosylmethionine; D003547:Cysteine Synthase; C103381:MET17 protein, S cerevisiae; C018725:O-acetylhomoserine (thiol)-lyase; D004262:DNA Restriction Enzymes; D008190:Lyases; D019757:Carbon-Oxygen Lyases