Distinct roles for argonaute proteins in small RNA-directed RNA cleavage pathways
Distinct roles for argonaute proteins in small RNA-directed RNA cleavage pathways
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DOI：
10.1101/gad.1210204
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发表时间：
2004-07-15
影响因子：
10.5
通讯作者：
Siomi, MC
中科院分区：
文献类型：
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作者：
Okamura, K;Ishizuka, A;Siomi, MC
在哺乳动物细胞中，microRNA（miRNAs）和小干扰RNA（siRNAs）被认为加载到相同的RNA诱导沉默复合物（RISC）中，在那里它们根据靶的互补性引导mRNA降解或翻译沉默。在果蝇中，Argonaute 2（AGO 2）被鉴定为RISC复合物的一部分。在这里，我们表明，AGO 2是siRNA指导的RNA干扰（RNAi）反应的一个重要组成部分，是必需的siRNA双链体的解旋，并在随后的装配成RISC的siRNA在果蝇胚胎。然而，缺乏AGO 2的果蝇胚胎，其是siRNA指导的RNAi缺陷的，仍然能够进行miRNA指导的靶RNA切割。与此相反，Argonaute 1（AGO 1），另一种Argonaute蛋白在苍蝇，这是siRNA指导的靶RNA切割，是需要成熟的miRNA生产，影响miRNA指导的RNA切割。AGO 1与Dicer-1和pre-miRNA的相关性也表明AGO 1参与了miRNA的生物合成。我们的研究结果表明，不同的Argonaute蛋白在小RNA沉默机制的不同步骤中发挥作用，并表明果蝇中SiRNA启动的RISC和miRNA启动的RISC之间存在固有差异。
In mammalian cells, both microRNAs (miRNAs) and small interfering RNAs (siRNAs) are thought to be loaded into the same RNA-induced silencing complex (RISC), where they guide mRNA degradation or translation silencing depending on the complementarity of the target. In Drosophila, Argonaute2 (AGO2) was identified as part of the RISC complex. Here we show that AGO2 is an essential component for siRNA-directed RNA interference (RNAi) response and is required for the unwinding of siRNA duplex and in consequence assembly of siRNA into RISC in Drosophila embryos. However, Drosophila embryos lacking AGO2, which are siRNA-directed RNAi-defective, are still capable of miRNA-directed target RNA cleavage. In contrast, Argonaute1 (AGO1), another Argonaute protein in fly, which is dispensable for siRNA-directed target RNA cleavage, is required for mature miRNA production that impacts on miRNA-directed RNA cleavage. The association of AGO1 with Dicer-1 and pre-miRNA also suggests that AGO1 is involved in miRNA biogenesis. Our findings show that distinct Argonaute proteins act at different steps of the small RNA silencing mechanism and suggest that there are inherent differences between siRNA-initiated RISCs and miRNA-initiated RISCs in Drosophila.