Vaquero Alejandro, Scher Michael, Lee Donghoon, Erdjument-Bromage Hediye, Tempst Paul, Reinberg Danny
Howard Hughes Medical Institute, Division of Nucleic Acids Enzymology, Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
Mol Cell. 2004 Oct 8;16(1):93-105. doi: 10.1016/j.molcel.2004.08.031.
We characterized human SirT1, one of the human homologs of the budding yeast Sir2p, an NAD+-dependent histone deacetylase involved in establishing repressive chromatin and increased life span. SirT1 deacetylates histone polypeptides with a preference for histone H4 lysine 16 (H4-K16Ac) and H3 lysine 9 (H3-K9Ac) in vitro. RNAi-mediated decreased expression of SirT1 in human cells causes hyperacetylation of H4-K16 and H3-K9 in vivo. SirT1 interacts with and deacetylates histone H1 at lysine 26. Using an inducible system directing expression of SirT1 fused to the Gal4-DNA binding domain and a Gal4-reporter integrated in euchromatin, Gal4-SirT1 expression resulted in the deacetylation of H4-K16 and H3-K9, recruitment of H1 within the promoter vicinity, drastically reduced reporter expression, and loss of H3-K79 methylation, a mark restricting silenced chromatin. We propose a model for SirT1-mediated heterochromatin formation that includes deacetylation of histone tails, recruitment and deacetylation of histone H1, and spreading of hypomethylated H3-K79 with resultant silencing.
我们对人类SirT1进行了表征，它是芽殖酵母Sir2p的人类同源物之一，是一种参与建立抑制性染色质和延长寿命的NAD+依赖性组蛋白脱乙酰酶。SirT1在体外可使组蛋白多肽去乙酰化，对组蛋白H4赖氨酸16（H4-K16Ac）和H3赖氨酸9（H3-K9Ac）具有偏好性。RNA干扰介导的人类细胞中SirT1表达降低会导致体内H4-K16和H3-K9的超乙酰化。SirT1与组蛋白H1的赖氨酸26相互作用并使其去乙酰化。使用一种诱导系统来指导与Gal4-DNA结合结构域融合的SirT1的表达以及整合在常染色质中的Gal4报告基因，Gal4-SirT1的表达导致H4-K16和H3-K9的去乙酰化、H1在启动子附近的募集、报告基因表达的大幅降低以及H3-K79甲基化的丧失，H3-K79甲基化是一种限制沉默染色质的标记。我们提出了一个SirT1介导的异染色质形成模型，该模型包括组蛋白尾巴的去乙酰化、组蛋白H1的募集和去乙酰化，以及低甲基化的H3-K79的扩散并导致沉默。
