title: Dicer recognizes the 5' end of RNA for efficient and accurate processing.
abstract: A hallmark of RNA silencing is a class of approximately 22-nucleotide RNAs that are processed from double-stranded RNA precursors by Dicer. Accurate processing by Dicer is crucial for the functionality of microRNAs (miRNAs). The current model posits that Dicer selects cleavage sites by measuring a set distance from the 3' overhang of the double-stranded RNA terminus. Here we report that human Dicer anchors not only the 3' end but also the 5' end, with the cleavage site determined mainly by the distance (∼22 nucleotides) from the 5' end (5' counting rule). This cleavage requires a 5'-terminal phosphate group. Further, we identify a novel basic motif (5' pocket) in human Dicer that recognizes the 5'-phosphorylated end. The 5' counting rule and the 5' anchoring residues are conserved in Drosophila Dicer-1, but not in Giardia Dicer. Mutations in the 5' pocket reduce processing efficiency and alter cleavage sites in vitro. Consistently, miRNA biogenesis is perturbed in vivo when Dicer-null embryonic stem cells are replenished with the 5'-pocket mutant. Thus, 5'-end recognition by Dicer is important for precise and effective biogenesis of miRNAs. Insights from this study should also afford practical benefits to the design of small hairpin RNAs.
authors.affiliation: School of Biological Sciences, Seoul National University, Seoul 151-742, Korea.
authors.forename: Jong-Eun
authors.initials: JE
authors.lastname: Park
authors.forename: Inha
authors.initials: I
authors.lastname: Heo
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Dhirendra K
authors.initials: DK
authors.lastname: Simanshu
authors.forename: Hyeshik
authors.initials: H
authors.lastname: Chang
authors.forename: David
authors.initials: D
authors.lastname: Jee
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
authors.forename: V Narry
authors.initials: VN
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D053487:DEAD-box RNA Helicases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism; D053595:Embryonic Stem Cells / Q000378:metabolism; D019143:Evolution, Molecular; D005872:Giardia / Q000201:enzymology; D057809:HEK293 Cells; D006801:Humans; D035683:MicroRNAs / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D020365:RNA Helicases / Q000378:metabolism; D043244:Ribonuclease III / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity / Q000235:genetics
chemical_list: D029721:Drosophila Proteins; D035683:MicroRNAs; D050505:Mutant Proteins; D010710:Phosphates; C515033:Dcr-1 protein, Drosophila; C408087:DICER1 protein, human; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases