title: Antiviral RNA silencing initiated in the absence of RDE-4, a double-stranded RNA binding protein, in Caenorhabditis elegans.
abstract: Small interfering RNAs (siRNAs) processed from double-stranded RNA (dsRNA) of virus origins mediate potent antiviral defense through a process referred to as RNA interference (RNAi) or RNA silencing in diverse organisms. In the simple invertebrate Caenorhabditis elegans, the RNAi process is initiated by a single Dicer, which partners with the dsRNA binding protein RDE-4 to process dsRNA into viral siRNAs (viRNAs). Notably, in C. elegans this RNA-directed viral immunity (RDVI) also requires a number of worm-specific genes for its full antiviral potential. One such gene is rsd-2 (RNAi spreading defective 2), which was implicated in RDVI in our previous studies. In the current study, we first established an antiviral role by showing that rsd-2 null mutants permitted higher levels of viral RNA accumulation, and that this enhanced viral susceptibility was reversed by ectopic expression of RSD-2. We then examined the relationship of rsd-2 with other known components of RNAi pathways and established that rsd-2 functions in a novel pathway that is independent of rde-4 but likely requires the RNA-dependent RNA polymerase RRF-1, suggesting a critical role for RSD-2 in secondary viRNA biogenesis, likely through coordinated action with RRF-1. Together, these results suggest that RDVI in the single-Dicer organism C. elegans depends on the collective actions of both RDE-4-dependent and RDE-4-independent mechanisms to produce RNAi-inducing viRNAs. Our study reveals, for the first time, a novel siRNA-producing mechanism in C. elegans that bypasses the need for a dsRNA-binding protein.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA.
authors.forename: Xunyang
authors.initials: X
authors.lastname: Guo
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Wang
authors.forename: Rui
authors.initials: R
authors.lastname: Lu
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D000998:Antiviral Agents / Q000494:pharmacology*; D015152:Blotting, Northern; D017173:Caenorhabditis elegans / Q000821:virology*; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D007304:Insect Viruses / Q000235:genetics*; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism
chemical_list: D000998:Antiviral Agents; D029742:Caenorhabditis elegans Proteins; C461645:RDE-4 protein, C elegans; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D012367:RNA, Viral; D016601:RNA-Binding Proteins; C529657:RSD-2 protein, C elegans; C122185:rde-1 protein, C elegans; D012324:RNA-Dependent RNA Polymerase; C574791:RRF-1 protein, C elegans