title: Distinct populations of primary and secondary effectors during RNAi in C. elegans.
abstract: RNA interference (RNAi) is a phylogenetically widespread gene-silencing process triggered by double-stranded RNA. In plants and Caenorhabditis elegans, two distinct populations of small RNAs have been proposed to participate in RNAi: "Primary siRNAs" (derived from DICER nuclease-mediated cleavage of the original trigger) and "secondary siRNAs" [additional small RNAs whose synthesis requires an RNA-directed RNA polymerase (RdRP)]. Analyzing small RNAs associated with ongoing RNAi in C. elegans, we found that secondary siRNAs constitute the vast majority. The bulk of secondary siRNAs exhibited structure and sequence indicative of a biosynthetic mode whereby each molecule derives from an independent de novo initiation by RdRP. Analysis of endogenous small RNAs indicated that a fraction derive from a biosynthetic mechanism that is similar to that of secondary siRNAs formed during RNAi, suggesting that small antisense transcripts derived from cellular messenger RNAs by RdRP activity may have key roles in cellular regulation.
authors.affiliation: Departments of Pathology and Genetics, Stanford University School of Medicine, Stanford, CA 94305-5324, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Pak
authors.forename: Andrew
authors.initials: A
authors.lastname: Fire
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D035683:MicroRNAs / Q000378:metabolism; D008957:Models, Genetic; D034622:RNA Interference; D016372:RNA, Antisense / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism; D018510:RNA, Helminth / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D035683:MicroRNAs; D016372:RNA, Antisense; D012330:RNA, Double-Stranded; D018510:RNA, Helminth; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012324:RNA-Dependent RNA Polymerase