The role of PACT in the RNA silencing pathway
The role of PACT in the RNA silencing pathway
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DOI：
10.1038/sj.emboj.7600942
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发表时间：
2006-02-08
期刊：
影响因子：
11.4
通讯作者：
Kim, VN
中科院分区：
文献类型：
--
作者：
Lee, Y;Hur, I;Kim, VN
小RNA介导的基因沉默（RNA沉默）已成为真核生物中的一个主要调控途径。近年来，对该途径中关键因子的鉴定一直是严格研究的课题。在人类中，小RNA由Dicer产生，并通过多种因子组装成效应复合物，即RNA诱导沉默复合物（RISC），这些因子包括靶向mRNA的内切核酸酶hAgo2以及与Dicer和hAgo2都相互作用的双链RNA结合蛋白TRBP（HIV - 1 TAR RNA结合蛋白）。在此我们描述了另一种名为PACT的双链RNA结合蛋白，它在RNA沉默中具有重要意义。PACT与一个约500 kDa的复合物相关联，该复合物包含Dicer、hAgo2和TRBP。与Dicer的相互作用涉及PACT的第三个双链RNA结合结构域（dsRBD）以及包含解旋酶基序的Dicer的N末端区域。与TRBP一样，PACT对于前体微小RNA（miRNA）的切割反应步骤不是必需的。然而，PACT的缺失强烈影响体内成熟miRNA的积累，并适度降低小干扰RNA诱导的RNA干扰效率。我们的研究表明，与其他RNase III型蛋白不同，人类Dicer可能利用两种不同的含dsRBD的蛋白来促进RISC组装。
Small RNA-mediated gene silencing ( RNA silencing) has emerged as a major regulatory pathway in eukaryotes. Identification of the key factors involved in this pathway has been a subject of rigorous investigation in recent years. In humans, small RNAs are generated by Dicer and assembled into the effector complex known as RNA-induced silencing complex ( RISC) by multiple factors including hAgo2, the mRNA-targeting endonuclease, and TRBP (HIV-1 TAR RNA-binding protein), a dsRNA-binding protein that interacts with both Dicer and hAgo2. Here we describe an additional dsRNA-binding protein known as PACT, which is significant in RNA silencing. PACT is associated with an similar to 500 kDa complex that contains Dicer, hAgo2, and TRBP. The interaction with Dicer involves the third dsRNA-binding domain (dsRBD) of PACT and the N-terminal region of Dicer containing the helicase motif. Like TRBP, PACT is not required for the pre-microRNA ( miRNA) cleavage reaction step. However, the depletion of PACT strongly affects the accumulation of mature miRNA in vivo and moderately reduces the efficiency of small interfering RNA-induced RNA interference. Our study indicates that, unlike other RNase III type proteins, human Dicer may employ two different dsRBD-containing proteins that facilitate RISC assembly.