title: A dual role of H4K16 acetylation in the establishment of yeast silent chromatin.
abstract: Discrete regions of the eukaryotic genome assume heritable chromatin structure that is refractory to transcription. In budding yeast, silent chromatin is characterized by the binding of the Silent Information Regulatory (Sir) proteins to unmodified nucleosomes. Using an in vitro reconstitution assay, which allows us to load Sir proteins onto arrays of regularly spaced nucleosomes, we have examined the impact of specific histone modifications on Sir protein binding and linker DNA accessibility. Two typical marks for active chromatin, H3K79(me) and H4K16(ac) decrease the affinity of Sir3 for chromatin, yet only H4K16(ac) affects chromatin structure, as measured by nuclease accessibility. Surprisingly, we found that the Sir2-4 subcomplex, unlike Sir3, has higher affinity for chromatin carrying H4K16(ac). NAD-dependent deacetylation of H4K16(ac) promotes binding of the SIR holocomplex but not of the Sir2-4 heterodimer. This function of H4K16(ac) cannot be substituted by H3K56(ac). We conclude that acetylated H4K16 has a dual role in silencing: it recruits Sir2-4 and repels Sir3. Moreover, the deacetylation of H4K16(ac) by Sir2 actively promotes the high-affinity binding of the SIR holocomplex.
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
authors.forename: Mariano
authors.initials: M
authors.lastname: Oppikofer
authors.forename: Stephanie
authors.initials: S
authors.lastname: Kueng
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Martino
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Soeroes
authors.forename: Susan M
authors.initials: SM
authors.lastname: Hancock
authors.forename: Jason W
authors.initials: JW
authors.lastname: Chin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fischle
authors.forename: Susan M
authors.initials: SM
authors.lastname: Gasser
mesh_terms: D000107:Acetylation; D000818:Animals; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly / Q000502:physiology; D051548:Histone Acetyltransferases / Q000378:metabolism* / Q000502:physiology*; D006657:Histones / Q000378:metabolism* / Q000502:physiology; D008239:Lysine / Q000378:metabolism; D008954:Models, Biological; D008958:Models, Molecular; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000378:metabolism / Q000502:physiology; D056565:Sirtuin 2 / Q000378:metabolism / Q000502:physiology; D018411:Spodoptera; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D002843:Chromatin; D006657:Histones; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D051548:Histone Acetyltransferases; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D008239:Lysine