Methylation protects microRNAs from an AGO1-associated activity that uridylates 5' RNA fragments generated by AGO1 cleavage
Methylation protects microRNAs from an AGO1-associated activity that uridylates 5' RNA fragments generated by AGO1 cleavage
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DOI：
10.1073/pnas.1405083111
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发表时间：
2014-04-29
影响因子：
11.1
通讯作者：
Yu, Bin
中科院分区：
文献类型：
--
作者：
Ren, Guodong;Xie, Meng;Yu, Bin
在植物中，由HEN 1（小RNA甲基转移酶）催化的甲基化防止了由尿苷化引发的microRNA（miRNAs）降解。甲基化如何在体内拮抗miRNA的尿苷酸化尚不清楚。此外，通过miRNA介导的RNA切割产生的5' RNA片段（5'片段）可以在植物和动物中被尿苷化。然而，这种修饰的生物学意义是未知的，酶尿苷酸化5'片段仍有待鉴定。在这里，我们报告说，在拟南芥中，HEN 1抑制因子1（HESO 1，一种miRNA核苷酸转移酶）使5'片段尿苷酸化，从而引发它们的降解。我们还发现，Argonaute 1（AGO 1），miRNA的效应蛋白，通过其Piwi/Argonaute/ Zwille和PIWI结构域与HESO 1相互作用，其分别结合miRNA的3'末端和切割靶mRNA。此外，HESO 1能够在体外使AGO 1结合的miRNA尿苷化。体内miRNA尿苷化需要hen 1中的功能性AGO 1，其中miRNA甲基化受损，表明HESO 1可以识别AGO 1复合物中的底物。在这些结果的基础上，我们提出甲基化是保护miRNA免受AGO 1相关HESO 1活性影响所必需的，HESO 1活性通常使5'片段尿苷酸化。
In plants, methylation catalyzed by HEN1 (small RNA methyl transferase) prevents microRNAs (miRNAs) from degradation triggered by uridylation. How methylation antagonizes uridylation of miRNAs in vivo is not well understood. In addition, 5' RNA fragments (5' fragments) produced by miRNA-mediated RNA cleavage can be uridylated in plants and animals. However, the biological significance of this modification is unknown, and enzymes uridylating 5' fragments remain to be identified. Here, we report that in Arabidopsis, HEN1 suppressor 1 (HESO1, a miRNA nucleotidyl transferase) uridylates 5' fragments to trigger their degradation. We also show that Argonaute 1 (AGO1), the effector protein of miRNAs, interacts with HESO1 through its Piwi/Argonaute/ Zwille and PIWI domains, which bind the 3' end of miRNA and cleave the target mRNAs, respectively. Furthermore, HESO1 is able to uridylate AGO1-bound miRNAs in vitro. miRNA uridylation in vivo requires a functional AGO1 in hen1, in which miRNA methylation is impaired, demonstrating that HESO1 can recognize its substrates in the AGO1 complex. On the basis of these results, we propose that methylation is required to protect miRNAs from AGO1-associated HESO1 activity that normally uridylates 5' fragments.