Argonaute Divides Its RNA Guide into Domains with Distinct Functions and RNA-Binding Properties

• Published in: Cell Vol. 151; no. 5; pp. 1055 - 1067
• Main Authors: Wee, Liang Meng, Flores-Jasso, C. Fabián, Salomon, William E., Zamore, Phillip D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21-11-2012
• Subjects: Animals; Argonaute 2 protein; Argonaute Proteins - chemistry; Argonaute Proteins - metabolism; Base Sequence; Complementarity; Data processing; Drosophila melanogaster - metabolism; Drosophila Proteins - chemistry; Drosophila Proteins - metabolism; Gene expression; messenger RNA; Mice; microRNA; MicroRNAs - metabolism; miRNA; Models, Biological; proteins; RNA Interference; RNA, Guide - metabolism; RNA, Small Interfering - metabolism; RNA-Induced Silencing Complex - metabolism; Seeds; siRNA; small interfering RNA; Tails
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2012.10.036

MicroRNAs (miRNAs) and small interfering RNAs (siRNAs) guide Argonaute proteins to silence mRNA expression. Argonaute binding alters the properties of an RNA guide, creating functional domains. We show that the domains established by Argonaute—the anchor, seed, central, 3′ supplementary, and tail regions—have distinct biochemical properties that explain the differences between how animal miRNAs and siRNAs bind their targets. Extensive complementarity between an siRNA and its target slows the rate at which fly Argonaute2 (Ago2) binds to and dissociates from the target. Highlighting its role in antiviral defense, fly Ago2 dissociates so slowly from extensively complementary target RNAs that essentially every fully paired target is cleaved. Conversely, mouse AGO2, which mainly mediates miRNA-directed repression, dissociates rapidly and with similar rates for fully paired and seed-matched targets. Our data narrow the range of biochemically reasonable models for how Argonaute-bound siRNAs and miRNAs find, bind, and regulate their targets.
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► Argonaute organizes its small RNA guide into functionally distinct domains ► GU pairs act like seed mismatches and should be disallowed in miRNA target prediction ► Fly but not mouse Ago2 dissociates slowly; virtually every bound target is cleaved ► Like RNA-binding proteins, miRNAs in Ago2 bind and leave their targets rapidly
Small RNA guides are organized into functional domains to silence complementary mRNAs by fly and mouse Argonautes, which respectively exhibit slow and fast kinetics of dissociation, thus defining the range of models for how small RNAs find, bind, and regulate their targets.