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首页> 外文期刊>Molecular and Cellular Biology >Steps in Assembly of Silent Chromatin in Yeast: Sir3-Independent Binding of a Sir2/Sir4 Complex to Silencers and Role for Sir2-Dependent Deacetylation
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Steps in Assembly of Silent Chromatin in Yeast: Sir3-Independent Binding of a Sir2/Sir4 Complex to Silencers and Role for Sir2-Dependent Deacetylation

机译：酵母中沉默染色质组装的步骤：Sir2 / Sir4复合物与沉默子的Sir3独立结合以及Sir2依赖性脱乙酰作用

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Transcriptional silencing at the budding yeast silent mating type (HM) loci and telomeric DNA regions requires Sir2, a conserved NAD-dependent histone deacetylase, Sir3, Sir4, histones H3 and H4, and several DNA-binding proteins. Silencing at the yeast ribosomal DNA (rDNA) repeats requires a complex containing Sir2, Net1, and Cdc14. Here we show that the native Sir2/Sir4 complex is composed solely of Sir2 and Sir4 and that native Sir3 is not associated with other proteins. We further show that the initial binding of the Sir2/Sir4 complex to DNA sites that nucleate silencing, accompanied by partial Sir2-dependent histone deacetylation, occurs independently of Sir3 and is likely to be the first step in assembly of silent chromatin at the HM loci and telomeres. The enzymatic activity of Sir2 is not required for this initial binding, but is required for the association of silencing proteins with regions distal from nucleation sites. At the rDNA repeats, we show that histone H3 and H4 tails are required for silencing and rDNA-associated H4 is hypoacetylated in a Sir2-dependent manner. However, the binding of Sir2 to rDNA is independent of its histone deacetylase activity. Together, these results support a stepwise model for the assembly of silent chromatin domains in Saccharomyces cerevisiae.
机译：在萌芽的酵母沉默交配型（ HM ）位点和端粒DNA区域进行转录沉默需要Sir2，一个保守的NAD依赖性组蛋白脱乙酰基酶，Sir3，Sir4，组蛋白H3和H4以及几种DNA结合蛋白。沉默酵母核糖体DNA（rDNA）重复序列需要包含Sir2，Net1和Cdc14的复合物。在这里，我们显示出天然的Sir2 / Sir4复合物仅由Sir2和Sir4组成，而天然的Sir3与其他蛋白质无关。我们进一步表明，Sir2 / Sir4复合物与核酸沉默的DNA位点的初始结合，伴随着部分Sir2依赖性组蛋白去乙酰化，独立于Sir3发生，并且很可能是组装沉默染色质的第一步。 > HM 基因座和端粒。 Sir2的酶促活性对于这种初始结合不是必需的，但是沉默蛋白与成核位点远端区域的缔合则是必需的。在rDNA重复序列中，我们显示了沉默需要组蛋白H3和H4尾部，并且与rDNA相关的H4以Sir2依赖性方式被低乙酰化。但是，Sir2与rDNA的结合独立于其组蛋白脱乙酰基酶活性。在一起，这些结果支持在酿酒酵母中的沉默染色质域组装的逐步模型。

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