Structural Flexibility Enables Alternative Maturation, ARGONAUTE Sorting and Activities of miR168, a Global Gene Silencing Regulator in Plants

作     者：Taichiro Iki Antoine Cléry Nicolas G. Bologna Alexis Sarazin Christopher A. Brosnan Nathan Pumplin Frédéric H.T. Allain Olivier Voinnet 

作者机构：Department of Biology Swiss Federal Institute of Technology (ETH) Universit&tstrasse 2 ZUrich 8092 Switzerland Institute of Molecular Biology and Biophysics Department of Biology Swiss Federal Institute of Technology (ETH) Zürich Switzerland Biomolecular NMR spectroscopy Platform ETH Zürich Switzerland Present address: Laboratory of Germline Biology Graduate School of Frontier Biosciences Osaka University 1-3 Yamadaoka Suita Osaka Japan 

出 版 物：《Molecular Plant》 (分子植物（英文版）)

年 卷 期：2018年第11卷第8期

页      面：1008-1023页

核心收录：

学科分类：0710[理学-生物学] 07[理学] 071007[理学-遗传学] 0901[农学-作物学] 0902[农学-园艺学] 0713[理学-生态学] 

基　　金：The NCCR RNA and disease funded by the Swiss National Science Foundation （SNF 51NF40_141735） for access to the Biomolecular NMR spectrometry platform at ETH ZUrich. This work was supported by an IIF Marie Curie fellowship to TI （no. 329029） and a European Research Council （ERC） advanced grant ＂Frontiers of RNAi-Ⅱ＂ to OV （no. 323071）. 

主　　题：microRNA miR168 Dicer ARGONAUTE tombusvirus P19 

摘      要：In eukaryotes, the RNase-Ⅲ Dicer often produces length/sequence microRNA （miRNA） variants, called ＂isomiRs＂, owing to intrinsic structural/sequence determinants of the miRNA precursors （pre-miRNAs）. In this study, we combined biophysics, genetics and biochemistry approaches to study Arabidopsis miR168, the key feedback regulator of central plant silencing effector protein ARGONAUTE1 （AGO1）. We identified a motif conserved among plant premiR168 orthologs, which enables flexible internal basepairing underlying at least three metastable structural configurations. These configurations promote alternative, accurate Dicer cleavage events generating length and structural isomiR168 variants with distinctive AGO sorting properties and modes of action. Among these isomiR168s, a duplex with a 22-nt guide strand exhibits strikingly preferential affinity for AGO10, the closest AGO1 paralog. The 22-nt miR168-AGO10 complex antagonizes AGO1 accumulation in part via ＂transitive RNAi＂, a silencing-amplification process, to maintain appropriate AGO1 cellular homeostasis. Furthermore, we found that the tombusviral P19 silencing-suppressor protein displays markedly weaker affinity for the 22-nt form among its isomiR168 cargoes, thereby promoting AGO10-directed suppression of AGOl-mediated antiviral silencing. Taken together, these findings indicate that structural flexibility, a previously overlooked property of premiRNAs, considerably increases the versatility and regulatory potential of individual MIRNA genes, and that some pathogens might have evolved the capacity or mechanisms to usurp this property.