title: Chromatin assembly factor Asf1p-dependent occupancy of the SAS histone acetyltransferase complex at the silent mating-type locus HMLalpha.
abstract: Transcriptional repression of the silent mating-type loci HMLalpha and HMRa in Saccharomyces cerevisiae is regulated by chromatin structure. Sas2p is a catalytic subunit of the SAS histone acetyltransferase (HAT) complex. Although many HATs seem to relieve chromosomal repression to facilitate transcriptional activation, sas mutant phenotypes include loss of SIR1-dependent silencing of HMLalpha. To gain insight into the mechanism of the SAS complex mediated silencing at HMLalpha, we investigated the expression and chromatin structure of the alpha2 gene in the HMLalpha locus. We found that deletion of SAS2 in combination with a null allele of SIR1 changed the chromatin structure of the precisely positioned nucleosome, which includes the mRNA start site of the alpha2 gene and derepressed alpha2 transcription. The Sas2p HAT domain was required for this silencing. Furthermore, chromatin immunoprecipitation analysis revealed that the SAS complex was associated with the HMLalpha locus, and ASF1 (which encodes chromatin assembly factor Asf1p), but not SIR1 and SIR2, was necessary for this localization. These data suggest that the HAT activity and ASF1-dependent localization of the SAS complex are required for SIR1-dependent HMLalpha silencing.
authors.affiliation: Laboratory of Environmental Biochemistry, Graduate School of Pharmaceutical Sciences, Osaka University 1-6 Yamada-Oka, Suita, Osaka 565-0871, Japan. osada@phs.osaka-u.ac.jp
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Osada
authors.forename: Mitsumasa
authors.initials: M
authors.lastname: Kurita
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Nishikawa
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nishihara
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D051548:Histone Acetyltransferases; D006655:Histone Deacetylases / Q000502:physiology; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000235:genetics*; D018832:Molecular Chaperones; D009707:Nucleosomes / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology; D056565:Sirtuin 2; D037761:Sirtuins / Q000502:physiology
chemical_list: C109731:ASF1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D018398:Homeodomain Proteins; C062928:MATA2 protein, S cerevisiae; D018832:Molecular Chaperones; D009707:Nucleosomes; D012097:Repressor Proteins; C084121:SIR1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; C469266:Sas2 protein, S cerevisiae; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases