A Seed Mismatch Enhances Argonaute2-Catalyzed Cleavage and Partially Rescues Severely Impaired Cleavage Found in Fish
A Seed Mismatch Enhances Argonaute2-Catalyzed Cleavage and Partially Rescues Severely Impaired Cleavage Found in Fish
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DOI：
10.1016/j.molcel.2017.11.032
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发表时间：
2017-12-21
期刊：
影响因子：
16
通讯作者：
Bartel, David P.
中科院分区：
文献类型：
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作者：
Chen, Grace R.;Sive, Hazel;Bartel, David P.
RNAi途径在许多真核生物物种中提供先天免疫和有效的基因敲低工具，但奇怪的是斑马鱼没有。我们发现RNAi在斑马鱼中效果较差，至少部分原因是argonaute2催化的mRNA切片受损。这种缺陷是由于在大多数硬骨鱼的祖先中出现的两个突变，这意味着大多数鱼缺乏有效的RNAi。尽管缺乏有效的切片活性，这些鱼保留了产生miR-451的能力，miR-451是一种由类似于切片的切割反应产生的microRNA。这种能力是由于鱼类miR-451前体中的G-G不匹配，这大大增强了其切割能力。类似的G-G错配（有时也是G-A错配）增强了目标切片，尽管破坏了对目标结合很重要的种子配对。这些结果为在斑马鱼中恢复RNAi提供了一种策略，并揭示了种子错配的意想不到的相反效应，以及对机制和指导rna设计的影响。
The RNAi pathway provides both innate immunity and efficient gene-knockdown tools in many eukaryotic species, but curiously not in zebrafish. We discovered that RNAi is less effective in zebrafish at least partly because Argonaute2-catalyzed mRNA slicing is impaired. This defect is due to two mutations that arose in an ancestor of most teleost fish, implying that most fish lack effective RNAi. Despite lacking efficient slicing activity, these fish have retained the ability to produce miR-451, a microRNA generated by a cleavage reaction analogous to slicing. This ability is due to a G-G mismatch within the fish miR-451 precursor, which substantially enhances its cleavage. An analogous G-G mismatch (or sometimes also a G-A mismatch) enhances target slicing, despite disrupting seed pairing important for target binding. These results provide a strategy for restoring RNAi to zebrafish and reveal unanticipated opposing effects of a seed mismatch with implications for mechanism and guide-RNA design.