title: Target RNA-directed trimming and tailing of small silencing RNAs.
abstract: In Drosophila, microRNAs (miRNAs) typically guide Argonaute1 to repress messenger RNA (mRNA), whereas small interfering RNAs (siRNAs) guide Argonaute2 to destroy viral and transposon RNA. Unlike siRNAs, miRNAs rarely form extensive numbers of base pairs to the mRNAs they regulate. We find that extensive complementarity between a target RNA and an Argonaute1-bound miRNA triggers miRNA tailing and 3'-to-5' trimming. In flies, Argonaute2-bound small RNAs--but not those bound to Argonaute1--bear a 2'-O-methyl group at their 3' ends. This modification blocks target-directed small RNA remodeling: In flies lacking Hen1, the enzyme that adds the 2'-O-methyl group, Argonaute2-associated siRNAs are tailed and trimmed. Target complementarity also affects small RNA stability in human cells. These results provide an explanation for the partial complementarity between animal miRNAs and their targets.
authors.affiliation: Howard Hughes Medical Institute and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Stefan L
authors.initials: SL
authors.lastname: Ameres
authors.forename: Michael D
authors.initials: MD
authors.lastname: Horwich
authors.forename: Jui-Hung
authors.initials: JH
authors.lastname: Hung
authors.forename: Jia
authors.initials: J
authors.lastname: Xu
authors.forename: Megha
authors.initials: M
authors.lastname: Ghildiyal
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Weng
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Zamore
mesh_terms: D000818:Animals; D060565:Argonaute Proteins; D020029:Base Pairing; D002460:Cell Line; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics; D039642:Eukaryotic Initiation Factors / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D012315:RNA Caps; D020871:RNA Stability; D018075:RNA, Complementary; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D034743:RNA-Induced Silencing Complex / Q000378:metabolism
chemical_list: C489654:AGO1 protein, Drosophila; C433807:AGO2 protein, Drosophila; D060565:Argonaute Proteins; D029721:Drosophila Proteins; D039642:Eukaryotic Initiation Factors; C531976:Let-7 microRNA, Drosophila; D035683:MicroRNAs; D012315:RNA Caps; D018075:RNA, Complementary; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D034743:RNA-Induced Silencing Complex; C471146:bantam microRNA, Drosophila; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; C521948:Hen1 protein, Drosophila; D008780:Methyltransferases