Dicer functions in RNA interference and in synthesis of small RNA involvedin developmental timing in C-elegans

Double-stranded RNAs can suppress expression of homologous genes through an evolutionarily conserved process named RNA interference (RNAi) or post-tra nscriptional gene silencing (PTGS). One mechanism underlying silencing is d egradation of target mRNAs by an RNP complex, which contains similar to 22 nt of siRNAs as guides to substrate selection. A bidentate nuclease called Dicer has been implicated as the protein responsible for siRNA production. Here we characterize the Caenorhabditis elegans ortholog of Dicer (K12H4.8; dcr-1) in vivo and in vitro. dcr-1 mutants show a defect in RNAi. Furtherm ore, a combination of phenotypic abnormalities and RNA analysis suggests a role for dcr-1 in a regulatory pathway comprised of small temporal RNA (let -7) and its target (e.g., lin-41).