ZFIN ID: ZDB-PUB-171223-9
A Seed Mismatch Enhances Argonaute2-Catalyzed Cleavage and Partially Rescues Severely Impaired Cleavage Found in Fish
Chen, G.R., Sive, H., Bartel, D.P.
Date: 2017
Source: Molecular Cell   68: 1095-1107.e5 (Journal)
Registered Authors: Sive, Hazel
Keywords: AGO2, Argonaute, RISC, RNAi, in vitro slicing, kinetic analysis, miR-451 processing, miRNA, siRNA design
MeSH Terms:
  • Animals
  • Argonaute Proteins/genetics
  • Argonaute Proteins/metabolism*
  • Base Pair Mismatch*
  • Gene Knockdown Techniques
  • Humans
  • MicroRNAs/genetics
  • MicroRNAs/metabolism*
  • RNA Interference*
  • RNA, Guide/genetics*
  • RNA, Messenger/genetics*
  • RNA, Messenger/metabolism
  • RNA-Induced Silencing Complex/genetics
  • RNA-Induced Silencing Complex/metabolism
  • Zebrafish/genetics*
  • Zebrafish/physiology
PubMed: 29272705 Full text @ Mol. Cell
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.