Inhibition of silencing and accelerated aging by nicotinamide, a putative negative regulator of yeast Sir2 and human SIRT1
Inhibition of silencing and accelerated aging by nicotinamide, a putative negative regulator of yeast Sir2 and human SIRT1
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DOI：
10.1074/jbc.m205670200
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发表时间：
2002-11-22
影响因子：
4.8
通讯作者：
Sinclair, DA
中科院分区：
文献类型：
--
作者：
Bitterman, KJ;Anderson, RM;Sinclair, DA
酿酒酵母 Sir2 蛋白是一种 NAD(+) 依赖性组蛋白脱乙酰酶，在转录沉默、基因组稳定性和寿命中发挥着关键作用。 Sir2 的人类同源物 SIRT1 可调节 p53 肿瘤抑制因子的活性并抑制细胞凋亡。 Sir2 脱乙酰反应产生两种产物：O-乙酰基-ADP-核糖和烟酰胺，烟酰胺是烟酸的前体，也是烟酸/维生素 B-3 的一种形式。我们在此表明，烟酰胺强烈抑制酵母沉默，增加 rDNA 重组，并将复制寿命缩短至 Sir2 突变体的复制寿命。即使在 G(1) 停滞的细胞中，烟酰胺也会消除沉默并导致 Sir2 最终离域，这表明沉默的异染色质需要持续的 Sir2 活性。我们发现生理浓度的烟酰胺在体外非竞争性抑制 Sir2 和 SIRT1。烟酰胺的抑制程度（IC50<50μM）等于或优于已知的此类蛋白质最有效的合成抑制剂。我们提出了一种模型，烟酰胺通过与 NAD(+) 相邻的保守口袋结合来抑制脱乙酰化，从而阻止 NAD(+) 水解。我们讨论烟酰胺是 Sir2 酶的生理相关调节剂的可能性。
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 (IC50 < 50 muM) 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.