Structural analysis of Stc1 provides insights into the coupling of RNAi and chromatin modification
Structural analysis of Stc1 provides insights into the coupling of RNAi and chromatin modification
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Stc1 的结构分析提供了对 RNAi 和染色质修饰耦合的见解
DOI：
10.1073/pnas.1212155110
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发表时间：
2013-05-21
影响因子：
11.1
通讯作者：
Bayne, Elizabeth H.
中科院分区：
文献类型：
--
作者：
He, Chao;Pillai, Sreerekha S.;Bayne, Elizabeth H.
非编码RNA可以通过直接修饰组蛋白改变染色质结构来调节基因表达。在分裂酵母中，通过RNAi途径产生的siRNA指导与异染色质形成相关的修饰。siRNA与RNAi效应蛋白Argonaute 1（Ago 1）结合，将含有Ago 1的RNA诱导的转录沉默（RITS）复合物靶向同源新生转录物。这促进了Clr 4复合物（CLRC）的募集，其介导同源染色质中赖氨酸9（H3 K9 me）上的组蛋白H3的甲基化。一个关键问题是RNAi和染色质修饰机制是如何连接的。Stc 1是一个小的蛋白质，最近被证明与Ago 1和CLRC，并发挥关键作用，介导的RNAi依赖的招募CLRC染色质。为了了解其作用模式，我们对Stc 1蛋白进行了详细的结构和功能分析。我们的分析表明，Stc 1的保守的N-末端区域代表一个不寻常的串联锌指结构域，与常见的LIM结构域的相似性，但区别在于缺乏两个锌指的优选相对取向。我们证明，这串联锌指结构域参与结合Ago 1，而非保守的C-末端区域介导协会与CLRC。这些发现阐明了RNAi与裂殖酵母染色质修饰偶联的分子基础。
Noncoding RNAs can modulate gene expression by directing modifications to histones that alter chromatin structure. In fission yeast, siRNAs produced via the RNAi pathway direct modifications associated with heterochromatin formation. siRNAs associate with the RNAi effector protein Argonaute 1 (Ago1), targeting the Ago1-containing RNA-induced transcriptional silencing (RITS) complex to homologous nascent transcripts. This promotes recruitment of the Clr4 complex (CLRC), which mediates methylation of histone H3 on lysine 9 (H3K9me) in cognate chromatin. A key question is how the RNAi and chromatin modification machineries are connected. Stc1 is a small protein recently shown to associate with both Ago1 and CLRC and to play a pivotal role in mediating the RNAi-dependent recruitment of CLRC to chromatin. To understand its mode of action, we have performed a detailed structural and functional analysis of the Stc1 protein. Our analyses reveal that the conserved N-terminal region of Stc1 represents an unusual tandem zinc finger domain, with similarities to common LIM domains but distinguished by a lack of preferred relative orientation of the two zinc fingers. We demonstrate that this tandem zinc finger domain is involved in binding Ago1, whereas the nonconserved C-terminal region mediates association with CLRC. These findings elucidate the molecular basis for the coupling of RNAi to chromatin modification in fission yeast.