title: Chemical activation of Sir2-dependent silencing by relief of nicotinamide inhibition.
abstract: Sir2 is a nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylase involved in gene silencing and longevity. Cellular stresses affect Sir2 activity, but the mechanisms of Sir2 regulation are debated. Nicotinamide has been proposed as a physiological regulator that inhibits Sir2 deacetylase activity by chemical reversal of a covalent reaction intermediate. We demonstrate a chemical strategy to activate Sir2-dependent transcriptional silencing and present evidence that the endogenous level of nicotinamide limits Sir2 activity in wild-type (wt) yeast cells. Nicotinamide inhibition of Sir2 is antagonized in vitro by isonicotinamide, which causes an increase in Sir2 deacetylation activity. Isonicotinamide also substantially increases transcriptional silencing at Sir2-regulated loci in wt strains and in strains lacking key NAD+ salvage pathway enzymes (PNC1 and NPT1). Thus, a nicotinamide antagonist is a Sir2 agonist in vitro and in vivo.
authors.affiliation: Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Sauve
authors.forename: Robyn D
authors.initials: RD
authors.lastname: Moir
authors.forename: Vern L
authors.initials: VL
authors.lastname: Schramm
authors.forename: Ian M
authors.initials: IM
authors.lastname: Willis
mesh_terms: D000107:Acetylation; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009536:Niacinamide / Q000378:metabolism / Q000494:pharmacology*; D009535:Nicotinamidase / Q000378:metabolism; D010430:Pentosyltransferases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000037:antagonists & inhibitors / Q000378:metabolism*; D056565:Sirtuin 2; D037761:Sirtuins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016615:Telomere / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D056572:Histone Deacetylase Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D009243:NAD; D009536:Niacinamide; C027681:isonicotinamide; D010430:Pentosyltransferases; C087778:SIR2 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D009535:Nicotinamidase; C474330:PNC1 protein, S cerevisiae; D006655:Histone Deacetylases; C021864:nicotinate phosphoribosyltransferase