Yigit Erbay, Batista Pedro J, Bei Yanxia, Pang Ka Ming, Chen Chun-Chieh G, Tolia Niraj H, Joshua-Tor Leemor, Mitani Shohei, Simard Martin J, Mello Craig C
Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
Cell. 2006 Nov 17;127(4):747-57. doi: 10.1016/j.cell.2006.09.033.
Argonaute (AGO) proteins interact with small RNAs to mediate gene silencing. C. elegans contains 27 AGO genes, raising the question of what roles these genes play in RNAi and related gene-silencing pathways. Here we describe 31 deletion alleles representing all of the previously uncharacterized AGO genes. Analysis of single- and multiple-AGO mutant strains reveals functions in several pathways, including (1) chromosome segregation, (2) fertility, and (3) at least two separate steps in the RNAi pathway. We show that RDE-1 interacts with trigger-derived sense and antisense RNAs to initiate RNAi, while several other AGO proteins interact with amplified siRNAs to mediate downstream silencing. Overexpression of downstream AGOs enhances silencing, suggesting that these proteins are limiting for RNAi. Interestingly, these AGO proteins lack key residues required for mRNA cleavage. Our findings support a two-step model for RNAi, in which functionally and structurally distinct AGOs act sequentially to direct gene silencing.
AGO蛋白与小RNA相互作用以介导基因沉默。秀丽隐杆线虫含有27个AGO基因，这就引发了一个问题，即这些基因在RNA干扰及相关基因沉默途径中发挥着什么作用。在此，我们描述了代表所有先前未表征的AGO基因的31个缺失等位基因。对单个和多个AGO突变菌株的分析揭示了其在多个途径中的功能，包括：（1）染色体分离；（2）生育力；以及（3）RNA干扰途径中的至少两个独立步骤。我们发现RDE-1与触发物衍生的正义和反义RNA相互作用以启动RNA干扰，而其他几种AGO蛋白则与扩增的小干扰RNA相互作用以介导下游沉默。下游AGO的过表达增强了沉默效果，这表明这些蛋白质是RNA干扰的限制因素。有趣的是，这些AGO蛋白缺乏mRNA切割所需的关键残基。我们的研究结果支持了RNA干扰的两步模型，其中功能和结构不同的AGO蛋白依次发挥作用以指导基因沉默。
