title: Structural insights into RNA processing by the human RISC-loading complex.
abstract: Targeted gene silencing by RNA interference (RNAi) requires loading of a short guide RNA (small interfering RNA (siRNA) or microRNA (miRNA)) onto an Argonaute protein to form the functional center of an RNA-induced silencing complex (RISC). In humans, Argonaute2 (AGO2) assembles with the guide RNA-generating enzyme Dicer and the RNA-binding protein TRBP to form a RISC-loading complex (RLC), which is necessary for efficient transfer of nascent siRNAs and miRNAs from Dicer to AGO2. Here, using single-particle EM analysis, we show that human Dicer has an L-shaped structure. The RLC Dicer's N-terminal DExH/D domain, located in a short 'base branch', interacts with TRBP, whereas its C-terminal catalytic domains in the main body are proximal to AGO2. A model generated by docking the available atomic structures of Dicer and Argonaute homologs into the RLC reconstruction suggests a mechanism for siRNA transfer from Dicer to AGO2.
authors.affiliation: Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA. hongwei.wang@yale.edu
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Cameron
authors.initials: C
authors.lastname: Noland
authors.forename: Bunpote
authors.initials: B
authors.lastname: Siridechadilok
authors.forename: David W
authors.initials: DW
authors.lastname: Taylor
authors.forename: Enbo
authors.initials: E
authors.lastname: Ma
authors.forename: Karin
authors.initials: K
authors.lastname: Felderer
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Doudna
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
mesh_terms: D060565:Argonaute Proteins; D015852:Eukaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D008854:Microscopy, Electron; D008954:Models, Biological; D011485:Protein Binding / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D034743:RNA-Induced Silencing Complex / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D043244:Ribonuclease III / Q000235:genetics / Q000648:ultrastructure; D000099253:Trans-Activation Responsive RNA-Binding Protein
chemical_list: D060565:Argonaute Proteins; D015852:Eukaryotic Initiation Factor-2; D035683:MicroRNAs; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D034743:RNA-Induced Silencing Complex; D043244:Ribonuclease III; D000099253:Trans-Activation Responsive RNA-Binding Protein; C466422:AGO2 protein, human