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RNA. 2010 May;16(5):893-903. doi: 10.1261/rna.2122010. Epub 2010 Mar 30.

Dicer's helicase domain is required for accumulation of some, but not all, C. elegans endogenous siRNAs.

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1
1Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA.

Abstract

Years after the discovery that Dicer is a key enzyme in gene silencing, the role of its helicase domain remains enigmatic. Here we show that this domain is critical for accumulation of certain endogenous small interfering RNAs (endo-siRNAs) in Caenorhabditis elegans. The domain is required for the production of the direct products of Dicer, or primary endo-siRNAs, and consequently affects levels of downstream intermediates, the secondary endo-siRNAs. Consistent with the role of endo-siRNAs in silencing, their loss correlates with an increase in cognate mRNA levels. We find that the helicase domain of Dicer is not necessary for microRNA (miRNA) processing, or RNA interference following exposure to exogenous double-stranded RNA. Comparisons of wild-type and helicase-defective strains using deep-sequencing analyses show that the helicase domain is required by a subset of annotated endo-siRNAs, in particular, those associated with the slightly longer 26-nucleotide small RNA species containing a 5' guanosine.

PMID:
20354150
PMCID:
PMC2856884
DOI:
10.1261/rna.2122010
[Indexed for MEDLINE]
Free PMC Article
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