2′-O-methylation stabilizes Piwi-associated small RNAs and ensures DNA elimination in Tetrahymena
2′-O-methylation stabilizes Piwi-associated small RNAs and ensures DNA elimination in Tetrahymena
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DOI：
10.1261/rna.1455509
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发表时间：
2009-04-01
期刊：
影响因子：
4.5
通讯作者：
Mochizuki, Kazufumi
中科院分区：
文献类型：
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作者：
Kurth, Henriette M.;Mochizuki, Kazufumi
小分子RNA（Small RNA）的长度约为20-30个核苷酸（nt），在转录和转录后水平调控基因的表达。在植物拟南芥中，所有的小RNA都被HEN 1的3 '-末端2'-O-甲基化，而在后生动物中只有一部分小RNA携带这种修饰。已知这种甲基化可以稳定小RNA，但其生物学意义尚不清楚。在纤毛虫原生动物嗜热四膜虫中，已经鉴定出两类小RNA：仅在有性生殖期间表达的与28-29 nt长（scnRNA）相似的RNA，以及组成型表达的与23-24 nt siRNA相似的RNA。在这项研究中，我们证明scnRNA（而不是siRNA）在其3'末端被2'-O-甲基化。四膜虫HEN 1同源物Hen 1 p负责scnRNA 2 '-O-甲基化。Hen 1 p的缺失导致scnRNA的水平和长度逐渐减少，程序化DNA消除的缺陷，以及有性后代的生产效率低下。因此，Hen 1 p介导的2 '-O-甲基化稳定了scnRNA，并确保了四膜虫中的DNA消除。这项研究清楚地表明，选定类别的小RNA上的3 '-末端2'-O-甲基化调节特定RNAi途径的功能。
Small RNAs similar to 20-30 nucleotides (nt) in length regulate gene expression at the transcriptional and post-transcriptional levels. In the plant Arabidopsis, all small RNAs are 3'-terminal 2'-O-methylated by HEN1, whereas only a subset of small RNAs carry this modification in metazoans. This methylation is known to stabilize small RNAs, but its biological significance remains unclear. In the ciliated protozoan Tetrahymena thermophila, two classes of small RNAs have been identified: RNAs similar to 28-29 nt long (scnRNAs) that are expressed only during sexual reproduction, and constitutively expressed similar to 23-24 nt siRNAs. In this study, we demonstrate that scnRNAs, but not siRNAs, are 2'-O-methylated at their 3' ends. The Tetrahymena HEN1 homolog Hen1p is responsible for scnRNA 2'-O-methylation. Loss of Hen1p causes a gradual reduction in the level and length of scnRNAs, defects in programmed DNA elimination, and inefficient production of sexual progeny. Therefore, Hen1p-mediated 2'-O-methylation stabilizes scnRNA and ensures DNA elimination in Tetrahymena. This study clearly shows that 3'-terminal 2'-O-methylation on a selected class of small RNAs regulates the function of a specific RNAi pathway.