Hakimi Mohamed-Ali, Bochar Daniel A, Schmiesing John A, Dong Yuanshu, Barak Orr G, Speicher David W, Yokomori Kyoko, Shiekhattar Ramin
The Wistar Institute, 3601 Spruce Street, Philadelphia, Pennsylvania 19104, USA.
Nature. 2002 Aug 29;418(6901):994-8. doi: 10.1038/nature01024.
Nucleosomal DNA is arranged in a higher-order structure that presents a barrier to most cellular processes involving protein DNA interactions. The cellular machinery involved in sister chromatid cohesion, the cohesin complex, also requires access to the nucleosomal DNA to perform its function in chromosome segregation. The machineries that provide this accessibility are termed chromatin remodelling factors. Here, we report the isolation of a human ISWI (SNF2h)-containing chromatin remodelling complex that encompasses components of the cohesin and NuRD complexes. We show that the hRAD21 subunit of the cohesin complex directly interacts with the ATPase subunit SNF2h. Mapping of hRAD21, SNF2h and Mi2 binding sites by chromatin immunoprecipitation experiments reveals the specific association of these three proteins with human DNA elements containing Alu sequences. We find a correlation between modification of histone tails and association of the SNF2h/cohesin complex with chromatin. Moreover, we show that the association of the cohesin complex with chromatin can be regulated by the state of DNA methylation. Finally, we present evidence pointing to a role for the ATPase activity of SNF2h in the loading of hRAD21 on chromatin.
核小体DNA以一种高阶结构排列，这种结构对大多数涉及蛋白质与DNA相互作用的细胞过程构成了障碍。参与姐妹染色单体黏连的细胞机制，即黏连蛋白复合体，也需要接触核小体DNA才能在染色体分离中发挥其功能。提供这种可及性的机制被称为染色质重塑因子。在这里，我们报告了一种包含人类ISWI（SNF2h）的染色质重塑复合体的分离，该复合体包含黏连蛋白和核小体去乙酰化酶复合体（NuRD）的组分。我们表明，黏连蛋白复合体的hRAD21亚基直接与ATP酶亚基SNF2h相互作用。通过染色质免疫沉淀实验对hRAD21、SNF2h和Mi2结合位点进行定位，揭示了这三种蛋白质与含有Alu序列的人类DNA元件的特异性结合。我们发现组蛋白尾巴的修饰与SNF2h/黏连蛋白复合体与染色质的结合之间存在相关性。此外，我们表明黏连蛋白复合体与染色质的结合可受DNA甲基化状态的调节。最后，我们提供的证据表明SNF2h的ATP酶活性在hRAD21加载到染色质上发挥作用。
