Uridylation of mature miRNAs and siRNAs by the MUT68 nucleotidyltransferase promotes their degradation in Chlamydomonas
Uridylation of mature miRNAs and siRNAs by the MUT68 nucleotidyltransferase promotes their degradation in Chlamydomonas
复制标题
DOI：
10.1073/pnas.0912632107
复制
发表时间：
2010-02-23
影响因子：
11.1
通讯作者：
Cerutti, Heriberto
中科院分区：
文献类型：
--
作者：
Ibrahim, Fadia;Rymarquis, Linda A.;Cerutti, Heriberto
在真核生物中，小RNA(长度类似于20-30个核苷酸)对基因表达的调控在发育途径和对基因组寄生虫的防御反应中起着至关重要的作用。微小RNAs(MiRNAs)和小干扰RNAs(SiRNAs)通常通过多种机制引导同源序列的失活，包括RNA降解、翻译抑制和转录抑制。最近的研究为miRNAs和siRNAs的生物发生和作用模式提供了相当多的见解。然而，对RNA干扰(RNAi)途径中的质量控制和小RNA衰变的机制知之甚少。在这里，我们证明了编码莱茵衣藻中末端核苷酸转移酶的MUT68的缺失，导致miRNA和siRNA水平升高。我们发现MUT68在体内小RNA 3‘端的非模板尿苷基化中起作用，并在体外通过RRP6外切体亚单位刺激其降解。此外，RRP6的耗尽还会导致小RNA在体内的积累。我们认为MUT68和RRP6在成熟的miRNAs和siRNAs的降解过程中相互合作，作为一种质量控制机制来消除功能失调或受损的小RNA分子。
Regulation of gene expression by small RNAs (similar to 20-30 nucleotides in length) plays an essential role in developmental pathways and defense responses against genomic parasites in eukaryotes. Micro-RNAs (miRNAs) and small interfering RNAs (siRNAs) commonly direct the inactivation of cognate sequences through a variety of mechanisms, including RNA degradation, translation inhibition, and transcriptional repression. Recent studies have provided considerable insight into the biogenesis and the mode of action of miRNAs and siRNAs. However, relatively little is known about mechanisms of quality control and small RNA decay in RNA interference (RNAi) pathways. Here we show that deletion of MUT68, encoding a terminal nucleotidyltransferase in the alga Chlamydomonas reinhardtii, results in elevated miRNA and siRNA levels. We found that MUT68 plays a role in the untemplated uridylation of the 3' ends of small RNAs in vivo and stimulates their degradation by the RRP6 exosome subunit in vitro. Moreover, RRP6 depletion also leads to accumulation of small RNAs in vivo. We propose that MUT68 and RRP6 cooperate in the degradation of mature miRNAs and siRNAs, as a quality control mechanism to eliminate dysfunctional or damaged small RNA molecules.