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Mol Cell. 2011 Apr 22;42(2):172-84. doi: 10.1016/j.molcel.2011.03.002. Epub 2011 Mar 17.

Phosphate and R2D2 restrict the substrate specificity of Dicer-2, an ATP-driven ribonuclease.

Author information

1
Department of Biochemistry and Molecular Pharmacology and Howard Hughes Medical Institute, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.

Abstract

Drosophila Dicer-2 generates small interfering RNAs (siRNAs) from long double-stranded RNA (dsRNA), whereas Dicer-1 produces microRNAs (miRNAs) from pre-miRNA. What makes the two Dicers specific for their biological substrates? We find that purified Dicer-2 can efficiently cleave pre-miRNA, but that inorganic phosphate and the Dicer-2 partner protein R2D2 inhibit pre-miRNA cleavage. Dicer-2 contains C-terminal RNase III domains that mediate RNA cleavage and an N-terminal helicase motif, whose function is unclear. We show that Dicer-2 is a dsRNA-stimulated ATPase that hydrolyzes ATP to ADP; ATP hydrolysis is required for Dicer-2 to process long dsRNA, but not pre-miRNA. Wild-type Dicer-2, but not a mutant defective in ATP hydrolysis, can generate siRNAs faster than it can dissociate from a long dsRNA substrate. We propose that the Dicer-2 helicase domain uses ATP to generate many siRNAs from a single molecule of dsRNA before dissociating from its substrate.

PMID:
21419681
PMCID:
PMC3115569
DOI:
10.1016/j.molcel.2011.03.002
[Indexed for MEDLINE]
Free PMC Article

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