title: 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.
authors: Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors: Jimmy J
authors: JJ
authors: Zhuang
authors: Stephen A
authors: SA
authors: Banse
authors: Craig P
authors: CP
authors: Hunter
mesh_terms: D000483:Alleles; D000818:Animals; D060565:Argonaute Proteins / Q000378:metabolism*; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D005095:Exoribonucleases / Q000378:metabolism; D005786:Gene Expression Regulation; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics
chemical_list: D060565:Argonaute Proteins; D029742:Caenorhabditis elegans Proteins; C530516:NRDE-3 protein, C elegans; C114543:PGL-1 protein, C elegans; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; C482202:ERI-1 protein, C elegans; D005095:Exoribonucleases