一种核糖核酸酶在RNA干扰过程中协调小干扰RNA的扩增和信使核糖核酸的切割。
A ribonuclease coordinates siRNA amplification and mRNA cleavage during RNAi.
作者信息
Tsai Hsin-Yue, Chen Chun-Chieh G, Conte Darryl, Moresco James J, Chaves Daniel A, Mitani Shohei, Yates John R, Tsai Ming-Daw, Mello Craig C
机构信息
RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA; Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan.
RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA 01605, USA.
出版信息
Cell. 2015 Jan 29;160(3):407-19. doi: 10.1016/j.cell.2015.01.010.
Effective silencing by RNA-interference (RNAi) depends on mechanisms that amplify and propagate the silencing signal. In some organisms, small-interfering RNAs (siRNAs) are amplified from target mRNAs by RNA-dependent RNA polymerase (RdRP). Both RdRP recruitment and mRNA silencing require Argonaute proteins, which are generally thought to degrade RNAi targets by directly cleaving them. However, in C. elegans, the enzymatic activity of the primary Argonaute, RDE-1, is not required for silencing activity. We show that RDE-1 can instead recruit an endoribonuclease, RDE-8, to target RNA. RDE-8 can cleave RNA in vitro and is needed for the production of 3' uridylated fragments of target mRNA in vivo. We also find that RDE-8 promotes RdRP activity, thereby ensuring amplification of siRNAs. Together, our findings suggest a model in which RDE-8 cleaves target mRNAs to mediate silencing, while generating 3' uridylated mRNA fragments to serve as templates for the RdRP-directed amplification of the silencing signal.
RNA干扰（RNAi）的有效沉默依赖于放大和传播沉默信号的机制。在某些生物体中，小干扰RNA（siRNA）通过RNA依赖的RNA聚合酶（RdRP）从靶mRNA中扩增而来。RdRP的招募和mRNA沉默都需要AGO蛋白，一般认为AGO蛋白通过直接切割来降解RNAi靶标。然而，在秀丽隐杆线虫中，主要的AGO蛋白RDE-1的酶活性对于沉默活性并非必需。我们发现，RDE-1反而可以招募一种核糖核酸内切酶RDE-8来作用于靶RNA。RDE-8能够在体外切割RNA，并且在体内靶mRNA的3'端尿苷酸化片段的产生过程中是必需的。我们还发现，RDE-8能促进RdRP活性，从而确保siRNA的扩增。总之，我们的研究结果提示了一种模型，即RDE-8切割靶mRNA以介导沉默，同时产生3'端尿苷酸化的mRNA片段作为RdRP指导的沉默信号扩增的模板。
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