title: Molecular insights into microRNA-mediated translational repression in plants.
abstract: microRNAs (miRNAs) bind Argonaute proteins in order to form RNA-induced silencing complexes (RISCs) that can silence the expression of complementary mRNAs. Plant miRNAs can mediate the cleavage of their target mRNAs as well as the repression of their translation. Here, by using an in vitro system prepared from plant culture cells, we biochemically dissect the mechanisms by which Arabidopsis thaliana ARGONAUTE1 RISC (AtAGO1-RISC) silences its mRNA targets. We find that AtAGO1-RISC has the ability to repress translation initiation without promoting deadenylation or mRNA decay. Strikingly, AtAGO1-RISC bound in the 5' untranslated region or the open reading frame can sterically block the recruitment or movement of ribosomes. These silencing effects require more extensive base pairing to the target site in comparison to typical animal miRNAs. Our data provide mechanistic insights into miRNA-mediated translational repression in plants.
authors.affiliation: Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
authors.forename: Hiro-oki
authors.initials: HO
authors.lastname: Iwakawa
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Tomari
mesh_terms: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002478:Cells, Cultured; D018506:Gene Expression Regulation, Plant; D035683:MicroRNAs / Q000235:genetics*; D016366:Open Reading Frames; D026723:Polyadenylation; D011485:Protein Binding; D014176:Protein Biosynthesis; D034622:RNA Interference; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D034743:RNA-Induced Silencing Complex / Q000378:metabolism; D014026:Nicotiana
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D029681:Arabidopsis Proteins; D035683:MicroRNAs; D012333:RNA, Messenger; D018749:RNA, Plant; D034743:RNA-Induced Silencing Complex