Beyond the seed: structural basis for supplementary microRNA targeting by human Argonaute2
Beyond the seed: structural basis for supplementary microRNA targeting by human Argonaute2
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DOI：
10.15252/embj.2018101153
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发表时间：
2019-07-01
期刊：
影响因子：
11.4
通讯作者：
MacRae, Ian J.
中科院分区：
文献类型：
--
作者：
Sheu-Gruttadauria, Jessica;Xiao, Yao;MacRae, Ian J.
microRNA（miRNAs）引导Argonaute蛋白质到靶向抑制的mRNA。靶标识别主要通过由引导（g）核苷酸g2-g8组成的miRNA种子区发生。然而，种子之外的核苷酸对于一些已知的miRNA-靶标相互作用也很重要。在这里，我们报告了人类Argonaute 2（Ago 2）的结构与通过miRNA种子和补充（g13-g16）区域识别的靶RNA接合。Ago 2创建了一个“补充室”，可容纳多达5个miRNA-靶碱基对。种子室和补充室彼此相邻，并且可以通过1-15个核苷酸的非结构化靶环桥接。补充室的打开可能受到miRNA 3 '尾中张力的限制，因为miRNA长度的增加稳定了补充相互作用。与以前的报道相反，我们证明了最佳的补充相互作用可以增加靶亲和力> 20倍。这些结果提供了一种延长miRNA靶向的机制，表明3 'isomiR在调节miRNA靶向特异性中的功能，并表明补充相互作用可能比广泛认识到的更有助于靶识别。
microRNAs (miRNAs) guide Argonaute proteins to mRNAs targeted for repression. Target recognition occurs primarily through the miRNA seed region, composed of guide (g) nucleotides g2-g8. However, nucleotides beyond the seed are also important for some known miRNA-target interactions. Here, we report the structure of human Argonaute2 (Ago2) engaged with a target RNA recognized through both miRNA seed and supplementary (g13-g16) regions. Ago2 creates a "supplementary chamber" that accommodates up to five miRNA-target base pairs. Seed and supplementary chambers are adjacent to each other and can be bridged by an unstructured target loop of 1-15 nucleotides. Opening of the supplementary chamber may be constrained by tension in the miRNA 3 ' tail, as increases in miRNA length stabilize supplementary interactions. Contrary to previous reports, we demonstrate that optimal supplementary interactions can increase target affinity > 20-fold. These results provide a mechanism for extended miRNA targeting, suggest a function for 3 ' isomiRs in tuning miRNA targeting specificity, and indicate that supplementary interactions may contribute more to target recognition than is widely appreciated.