title: SIR2 modifies histone H4-K16 acetylation and affects superhelicity in the ARS region of plasmid chromatin in Saccharomyces cerevisiae.
abstract: The null mutation of the SIR2 gene in Saccharomyces cerevisiae has been associated with a series of different phenotypes including loss of transcriptional silencing, genome instability and replicative aging. Thus, the SIR2 gene product is an important constituent of the yeast cell. SIR2 orthologues and paralogues have been discovered in organisms ranging from bacteria to man, underscoring the pivotal role of this protein. Here we report that a plasmid introduced into sir2Delta cells accumulates more negative supercoils compared to the same plasmid introduced into wild-type (WT) cells. This effect appears to be directly related to SIR2 expression as shown by the reduction of negative supercoiling when SIR2 is overexpressed, and does not depend on the number or positioning of nucleosomes on plasmids. Our results indicate that this new phenotype is due to the lack of Sir2p histone deacetylase activity in the sir2Delta strain, because only the H4-K16 residue of the histone octamer undergoes an alteration of its acetylation state. A model proposing interference with the replication machinery is discussed.
authors.affiliation: Dipartimento di Genetica e Biologia Molecolare, Università di Roma La Sapienza, Rome, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Chiani
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Felice
authors.forename: Giorgio
authors.initials: G
authors.lastname: Camilloni
mesh_terms: D000107:Acetylation; D018797:Cell Cycle Proteins / Q000235:genetics; D002843:Chromatin / Q000737:chemistry*; D004278:DNA, Superhelical / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000235:genetics; D017353:Gene Deletion; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism; D064168:Minichromosome Maintenance Complex Component 7; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000235:genetics; D009707:Nucleosomes / Q000737:chemistry; D010957:Plasmids / Q000737:chemistry*; D018741:Replication Origin; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D056565:Sirtuin 2; D037761:Sirtuins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D006657:Histones; D009687:Nuclear Proteins; D009707:Nucleosomes; C084122:SIR3 protein, S cerevisiae; C061573:SIR4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases; C491088:MCM7 protein, S cerevisiae; D064168:Minichromosome Maintenance Complex Component 7; D008239:Lysine