Dicer's helicase domain is required for accumulation of some, but not all, C. elegans endogenous siRNAs.
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.
Welker
Noah C
NC
1Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA.
Pavelec
Derek M
DM
Nix
David A
DA
Duchaine
Thomas F
TF
Kennedy
Scott
S
Bass
Brenda L
BL
D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D017238:Genes, Helminth; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional; D018510:RNA, Helminth / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics* / Q000378:metabolism*; D043244:Ribonuclease III / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D035683:MicroRNAs; D018510:RNA, Helminth; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D043244:Ribonuclease III; D020365:RNA Helicases