Authors: Bitterman KJ; Anderson RM; Cohen HY; Latorre-Esteves M; Sinclair DA
Abstract: The Saccharomyces cerevisiae Sir2 protein is an NAD(+)-dependent histone deacetylase that plays a critical role in transcriptional silencing, genome stability, and longevity. A human homologue of Sir2, SIRT1, regulates the activity of the p53 tumor suppressor and inhibits apoptosis. The Sir2 deacetylation reaction generates two products: O-acetyl-ADP-ribose and nicotinamide, a precursor of nicotinic acid and a form of niacin/vitamin B(3). We show here that nicotinamide strongly inhibits yeast silencing, increases rDNA recombination, and shortens replicative life span to that of a sir2 mutant. Nicotinamide abolishes silencing and leads to an eventual delocalization of Sir2 even in G(1)-arrested cells, demonstrating that silent heterochromatin requires continual Sir2 activity. We show that physiological concentrations of nicotinamide noncompetitively inhibit both Sir2 and SIRT1 in vitro. The degree of inhibition by nicotinamide (IC(50) < 50 microm) is equal to or better than the most effective known synthetic inhibitors of this class of proteins. We propose a model whereby nicotinamide inhibits deacetylation by binding to a conserved pocket adjacent to NAD(+), thereby blocking NAD(+) hydrolysis. We discuss the possibility that nicotinamide is a physiologically relevant regulator of Sir2 enzymes.
Keywords: Aging/*physiology; DNA, Ribosomal/genetics; *Gene Silencing; Genes, Fungal; Green Fluorescent Proteins; Histone Deacetylases/genetics/*metabolism; Humans; Life Expectancy; Luminescent Proteins/genetics/metabolism; Models, Biological; Molecular Structure; Niacinamide/*pharmacology; Recombinant Fusion Proteins/genetics/metabolism; Recombination, Genetic; Saccharomyces cerevisiae/*drug effects/genetics/physiology; Silent Information Regulator Proteins, Saccharomyces; cerevisiae/genetics/*metabolism; Sirtuin 1; Sirtuin 2; Sirtuins/genetics/*metabolism; Telomere/genetics|
Journal: The Journal of biological chemistry Volume: 277 Issue: 47 Pages: 45099-107 Date: Sept. 26, 2002 PMID: 12297502 |
Bitterman KJ, Anderson RM, Cohen HY, Latorre-Esteves M, Sinclair DA (2002) Inhibition of silencing and accelerated aging by nicotinamide, a putative negative regulator of yeast sir2 and human SIRT1. The Journal of biological chemistry 277: 45099-107.
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