The nuclear argonaute NRDE-3 contributes to transitive RNAi in Caenorhabditis elegans.

ABSTRACT: The Caenorhabditis elegans nuclear RNA interference defective (Nrde) mutants were identified by their inability to silence polycistronic transcripts in enhanced RNAi (Eri) mutant backgrounds. Here, we report additional nrde-3-dependent RNAi phenomena that extend the mechanisms, roles, and functions of nuclear RNAi. We show that nrde-3 mutants are broadly RNAi deficient and that overexpressing NRDE-3 enhances RNAi. Consistent with NRDE-3 being a dose-dependent limiting resource for effective RNAi, we find that NRDE-3 is required for eri-dependent enhanced RNAi phenotypes, although only for a subset of target genes. We then identify pgl-1 as an additional limiting RNAi resource important for eri-dependent silencing of a nonoverlapping subset of target genes, so that an nrde-3; pgl-1; eri-1 triple mutant fails to show enhanced RNAi for any tested gene. These results suggest that nrde-3 and pgl-1 define separate and independent limiting RNAi resource pathways. Limiting RNAi resources are proposed to primarily act via endogenous RNA silencing pathways. Consistent with this, we find that nrde-3 mutants misexpress genes regulated by endogenous siRNAs and incompletely silence repetitive transgene arrays. Finally, we find that nrde-3 contributes to transitive RNAi, whereby amplified silencing triggers act in trans to silence sequence-similar genes. Because nrde-dependent silencing is thought to act in cis to limit the production of primary transcripts, this result reveals an unexpected role for nuclear processes in RNAi silencing.

SUBMITTER: Zhuang JJ 

PROVIDER: S-EPMC3632460 | biostudies-literature | 2013 May

REPOSITORIES: biostudies-literature