Two different Argonaute complexes are required for siRNA generation and heterochromatin assembly in fission yeast
Two different Argonaute complexes are required for siRNA generation and heterochromatin assembly in fission yeast
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DOI：
10.1038/nsmb1211
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发表时间：
2007-03-01
影响因子：
16.8
通讯作者：
Moazed, Danesh
中科院分区：
文献类型：
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作者：
Buker, Shane M.;Iida, Tetsushi;Moazed, Danesh
rna诱导转录沉默（RITS）复合体包含Ago1、Chp1、Tas3和着丝粒小干扰rna (sirna)，是着丝粒异染色质基因沉默所必需的。在这里，我们鉴定了第二种裂变酵母Argonaute复合体（Argonaute siRNA chaperone， ARC），除了Ago1外，它还含有两种以前未被发现的蛋白质Arb1和Arb2，这两种蛋白质都是组蛋白H3 Lys9 （H3- k9）甲基化、异染色质组装和siRNA生成所必需的。此外，RITS复合体中的siRNA大多是单链的，而与ARC相关的siRNA大多是双链的，这表明Arb1和Arb2抑制了ago2中siRNA客链的释放。与这一观察结果一致，纯化的Arb1在体外抑制Ago1的切片活性，纯化的催化无活性Ago1只含有双链siRNA。最后，我们证明了ago2与染色质的sirna依赖性关联以及组蛋白H3-K9甲基化的扩散需要切片机活性。
The RNA-induced transcriptional silencing (RITS) complex, containing Ago1, Chp1, Tas3 and centromeric small interfering RNAs (siRNAs), is required for heterochromatic gene silencing at centromeres. Here, we identify a second fission yeast Argonaute complex ( Argonaute siRNA chaperone, ARC), which contains, in addition to Ago1, two previously uncharacterized proteins, Arb1 and Arb2, both of which are required for histone H3 Lys9 (H3-K9) methylation, heterochromatin assembly and siRNA generation. Furthermore, whereas siRNAs in the RITS complex are mostly single-stranded, siRNAs associated with ARC are mostly doublestranded, indicating that Arb1 and Arb2 inhibit the release of the siRNA passenger strand from Ago1. Consistent with this observation, purified Arb1 inhibits the slicer activity of Ago1 in vitro, and purified catalytically inactive Ago1 contains only double-stranded siRNA. Finally, we show that slicer activity is required for the siRNA-dependent association of Ago1 with chromatin and for the spreading of histone H3-K9 methylation.