Elements Involved in S-Adenosylmethionine-Mediated Regulation of the Saccharomyces cerevisiae MET25 Gene

Abstract

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.

Metabolism of sulfur amino acids in Saccharomyces cerevisiae.

“…Their participation in transcription activation was further supported by cloning an oligonucleotide containing one of these copies together with its adjacent nucleotides (spanning nucleotides Ϫ310 to Ϫ288 of the MET25 upstream region) in place of several of the deletions described above. In each case, CA CGTG and its adjacent nucleotides allowed MET25 transcription to be reacquired (246). The functional relevance of this sequence in the transcriptional regulation of sulfur metabolism was further supported by the finding of one or two copies of closely related sequences in the upstream regions of all the pathway structural genes (Fig.…”

“…As mentioned above, analysis of the MET25 upstream region pointed to the existence of another cis-acting element in addition to the TCACGTG sequence. Deletion of nucleotides around position Ϫ200 impaired the repression of MET25 transcription twofold (246). The Ϫ200 region of MET25 contains a short sequence, AAANTGTG, which is found in almost all the MET genes (Fig.…”

“…The first identification of DNA sequences that might mediate specific regulation of the MET genes was established through deletion analysis of the MET25 upstream region after growth under nonrepressive and repressive conditions (246). MET25 was chosen for this analysis because both the 5Ј end and half-life of its mRNA were known.…”

Chromatin Structure Modulation in Saccharomyces cerevisiae by Centromere and Promoter Factor 1

“…Probe DNA. The MET25 end label was derived from pM25-17, a gift from Y. Surdin-Kerjan (47). The MET25 5' region probes were derived from pSPMET25.…”

“…Interestingly, the CDEI motif is found at many other sites in the yeast genome, including gene regulatory sequences. The motif occurs in a diverse range of promoters including TRPJ, GAL2, and the promoters of several coregulated genes of the methionine biosynthetic pathway, including ME725, MET16, MET2, MET14, MET8, MET3, and SAM2 (5,8,29,30,46,47). It has been suggested that CPF1 associates with these sites and plays a role in transcriptional activation (2,5,6,34).…”