title: REP3-mediated silencing in Saccharomyces cerevisiae.
abstract: In yeast the Sir proteins and Rap1p are key regulators of transcriptional silencing at telomeres and the silent mating-type loci. Rap1 and Sir4 also possess anchoring activity; the rotation of plasmids bound by Sir4 or Rap1 is constrained in vivo, and Rap1 or Sir4 binding can also correct the segregation bias of plasmids lacking centromeres. To investigate the mechanistic link between DNA anchoring and regulation of transcription, we examined the ability of a third defined anchor in yeast, the 2micro circle REP3 segregation element, to mediate transcriptional silencing. We find that placement of the REP3 sequence adjacent to the HML locus in a strain deleted for natural silencer sequences confers transcriptional repression on HML. This repression requires the Sir proteins and is decreased in strains lacking the REP3-binding factors Rep1 and Rep2. The yeast cohesin complex associates with REP3; we show that REP3 silencing is also decreased in strains bearing a mutated allele of the MCD1/SCC1 cohesin gene. Conventional silencing is increased in some strains lacking the 2micro circle and decreased in strains overexpressing the Rep1 and Rep2 proteins, suggesting that the Rep proteins antagonize conventional silencing.
authors.affiliation: Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, Connecticut 06459, USA.
authors.forename: Laurie Ann
authors.initials: LA
authors.lastname: Papacs
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.forename: Erica L
authors.initials: EL
authors.lastname: Anderson
authors.forename: Jianjun
authors.initials: J
authors.lastname: Sun
authors.forename: Scott G
authors.initials: SG
authors.lastname: Holmes
mesh_terms: D001483:Base Sequence; D004271:DNA, Fungal / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020868:Gene Silencing; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D010957:Plasmids / Q000235:genetics; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D018741:Replication Origin; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D011498:Protein Precursors; C491137:REP1 protein, S cerevisiae; C490689:REP2 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators