title: On the Mechanism of Gene Silencing in Saccharomyces cerevisiae.
abstract: Multiple mechanisms have been proposed for gene silencing in Saccharomyces cerevisiae, ranging from steric occlusion of DNA binding proteins from their recognition sequences in silenced chromatin to a specific block in the formation of the preinitiation complex to a block in transcriptional elongation. This study provided strong support for the steric occlusion mechanism by the discovery that RNA polymerase of bacteriophage T7 could be substantially blocked from transcribing from its cognate promoter when embedded in silenced chromatin. Moreover, unlike previous suggestions, we found no evidence for stalled RNA polymerase II within silenced chromatin. The effectiveness of the Sir protein-based silencing mechanism to block transcription activated by Gal4 at promoters in the domain of silenced chromatin was marginal, yet it improved when tested against mutant forms of the Gal4 protein, highlighting a role for specific activators in their sensitivity to gene silencing.
authors.affiliation: Department of Molecular and Cell Biology, California Institute of Quantitative Biosciences, Stanley Hall, University of California Berkeley, Berkeley, California 94720.
authors.forename: David Lee
authors.initials: DL
authors.lastname: Steakley
authors.affiliation: Department of Molecular and Cell Biology, California Institute of Quantitative Biosciences, Stanley Hall, University of California Berkeley, Berkeley, California 94720 jrine@berkeley.edu.
authors.forename: Jasper
authors.initials: J
authors.lastname: Rine
mesh_terms: D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020868:Gene Silencing; D009841:Oligonucleotides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C052130:GAL4 protein, S cerevisiae; D009841:Oligonucleotides; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D014157:Transcription Factors; D012319:RNA Polymerase II
keywords: euchromatin; eukaryotic gene regulation; heterochromatin; repression; transcription