The Ku complex in silencing the cryptic mating-type loci of Saccharomyces cerevisiae.
Sir1 establishes transcriptional silencing at the cryptic mating-type loci HMR and HML (HM loci) by recruiting the three other Sir proteins, Sir2, -3, and -4, that function directly in silenced chromatin. However, SIR1-independent mechanisms also contribute to recruiting the Sir2-4 proteins to the HM loci. A screen to elucidate SIR1-independent mechanisms that establish HMR silencing identified a mutation in YKU80. The role for Ku in silencing both HMR and HML was masked by SIR1. Ku's role in silencing the HM loci was distinct from its shared role with the nuclear architecture protein Esc1 in tethering the HM loci and telomeres to the nuclear periphery. The ability of high-copy SIR4 to rescue HMR silencing defects in sir1Delta cells required Ku, and chromatin immunoprecipitation (ChIP) experiments provided evidence that Ku contributed to Sir4's physical association with the HM loci in vivo. Additional ChIP experiments provided evidence that Ku functioned directly at the HM loci. Thus Ku and Sir1 had overlapping roles in silencing the HM loci.
Patterson
Erin E
EE
Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706-1532, USA.
Fox
Catherine A
CA
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D009154:Mutation; D009687:Nuclear 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
C076558:CLB5 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D004268:DNA-Binding Proteins; C495981:Esc1 protein, S cerevisiae; C464906:Fkh1 protein, S cerevisiae; D051858:Forkhead Transcription Factors; D009687:Nuclear Proteins; C084121:SIR1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C520769:YKU70 protein, S cerevisiae; C520770:YKU80 protein, S cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae