title: The molecular architecture of human Dicer.
abstract: Dicer is a multidomain enzyme that generates small RNAs for gene silencing in eukaryotes. Current understanding of Dicer structure is restricted to simple forms of the enzyme, whereas that of the large and complex Dicer in metazoans is unknown. Here we describe a new domain localization strategy developed to determine the structure of human Dicer by EM. A rearrangement of the nuclease core, compared to the archetypal Giardia lamblia Dicer, explains how metazoan Dicers generate products that are 21-23 nucleotides in length. The helicase domains form a clamp-like structure adjacent to the RNase III active site, facilitating recognition of pre-miRNA loops or translocation on long dsRNAs. Drosophila melanogaster Dicer-2 shows similar features, revealing that the three-dimensional architecture is conserved. These results illuminate the structural basis for small RNA production in eukaryotes and provide a versatile new tool for determining structures of large molecular machines.
authors.affiliation: National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, California, USA.
authors.forename: Pick-Wei
authors.initials: PW
authors.lastname: Lau
authors.forename: Keelan Z
authors.initials: KZ
authors.lastname: Guiley
authors.forename: Nabanita
authors.initials: N
authors.lastname: De
authors.forename: Clinton S
authors.initials: CS
authors.lastname: Potter
authors.forename: Bridget
authors.initials: B
authors.lastname: Carragher
authors.forename: Ian J
authors.initials: IJ
authors.lastname: MacRae
mesh_terms: D000818:Animals; D053487:DEAD-box RNA Helicases / Q000737:chemistry* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000737:chemistry / Q000201:enzymology; D016829:Giardia lamblia / Q000737:chemistry / Q000201:enzymology; D006801:Humans; D008854:Microscopy, Electron / Q000379:methods; D008958:Models, Molecular; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D043244:Ribonuclease III / Q000737:chemistry* / Q000378:metabolism; D012260:Ribonucleases / Q000737:chemistry / Q000378:metabolism
chemical_list: D012313:RNA; D012260:Ribonucleases; C408087:DICER1 protein, human; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases