Target RNA-directed trimming and tailing of small silencing RNAs

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology; Program in Bioinformatics and Integrative Biology



Document Type


Medical Subject Headings

Animals; Argonaute Proteins; *Base Pairing; Cell Line; Drosophila Proteins; Drosophila melanogaster; Eukaryotic Initiation Factors; Green Fluorescent Proteins; Humans; Methylation; Methyltransferases; MicroRNAs; Models, Biological; RNA Caps; *RNA Stability; RNA, Complementary; RNA, Messenger; RNA, Small Interfering; RNA-Induced Silencing Complex


Computational Biology | Molecular Biology | Molecular Genetics


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.

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Citation: Science. 2010 Jun 18;328(5985):1534-9. doi: 10.1126/science.1187058. Link to article on publisher's site

Related Resources

Link to Article in PubMed