Article: article from journal or magazin.
Cooperation at a distance between silencers and proto-silencers at the yeast HML locus.
Publication types: Journal Article
Transcriptional repression at the silent yeast mating type loci is achieved through the formation of a particular nucleoprotein complex at specific cis-acting elements called silencers. This complex in turn appears to initiate the spreading of a histone binding protein complex into the surrounding chromatin, which restricts accessibility of the region to the transcription machinery. We have investigated long-range, cooperative effects between silencers by studying the repression of a reporter gene integrated at the HML locus flanked by various combinations of wild-type and mutated silencer sequences. Two silencers can cooperate over >4000 bp to repress transcription efficiently. More importantly, a single binding site for either the repressor activator protein 1 (Rap1), the autonomous replicating sequence (ARS) binding factor 1 (Abf1) or the origin recognition complex (ORC) can enhance the action of a distant silencer without acting as a silencer on its own. Functional cooperativity is demonstrated using a quantitative assay for repression, and varies with the affinity of the binding sites used. Since the repression mechanism is Sir dependent, the Rap1, ORC and/or Abf1 proteins bound to distant DNA elements may interact to create an interface of sufficiently high affinity such that Sir-containing complexes bind, nucleating the silent chromatin state.
Base Sequence, Binding Sites, DNA-Binding Proteins/metabolism, Fungal Proteins/metabolism, GTP-Binding Proteins/metabolism, Histone Deacetylases, Molecular Sequence Data, Oligodeoxyribonucleotides, Protein Binding, Saccharomyces cerevisiae/genetics, Silent Information Regulator Proteins, Saccharomyces cerevisiae, Sirtuins, Trans-Activators/metabolism, Transcription, Genetic, beta-Galactosidase/genetics, rap GTP-Binding Proteins
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