title: An enzymatic activity in the yeast Sir2 protein that is essential for gene silencing.
abstract: Despite its conservation in organisms from bacteria to human and its general requirement for transcriptional silencing in yeast, the function of the Sir2 protein is unknown. Here we show that Sir2 can transfer labeled phosphate from nicotinamide adenine dinucleotide to itself and histones in vitro. A modified form of Sir2, which results from its automodification activity, is specifically recognized by anti-mono-ADP-ribose antibodies, suggesting that Sir2 is an ADP-ribosyltransferase. Mutation of a phylogenetically invariant histidine residue in Sir2 abolishes both its enzymatic activity in vitro and its silencing functions in vivo. However, the mutant protein is associated with chromatin and other silencing factors in a manner similar to wild-type Sir2. These findings suggest that Sir2 contains an ADP-ribosyltransferase activity that is essential for its silencing function.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Tanny
authors.forename: G J
authors.initials: GJ
authors.lastname: Dowd
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: H
authors.initials: H
authors.lastname: Hilz
authors.forename: D
authors.initials: D
authors.lastname: Moazed
mesh_terms: D000595:Amino Acid Sequence; D015153:Blotting, Western; D002843:Chromatin / Q000378:metabolism; D004275:DNA, Ribosomal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing / Q000502:physiology*; D005800:Genes, Fungal; D006655:Histone Deacetylases; D006657:Histones / Q000378:metabolism; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011233:Precipitin Tests; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056564:Sirtuin 1; D056565:Sirtuin 2; D037761:Sirtuins; D016615:Telomere / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism*
chemical_list: D002843:Chromatin; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006657:Histones; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D009243:NAD; D011065:Poly(ADP-ribose) Polymerases; C087778:SIR2 protein, S cerevisiae; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases