Abstract
RNA interference (RNAi) is a post-transcriptional gene regulatory mechanism that operates in many eukaryotes. RNAi is induced by double-stranded RNA (dsRNA) and is mainly involved in defence against transposons and viruses. To counteract RNAi, viruses have RNAi suppressors. We present a novel mechanism of RNAi suppression by a plant virus Red clover necrotic mosaic virus(RCNMV). To suppress RNAi, RCNMV needs viral RNAs in addition to p27 and p88, which are putative RNA replicase components. Strong relationship between RNA elements required for minus-stranded RNA synthesis and RNAi suppression suggests a strong link between viral RNA replication machinery and RNAi machinery. In addition, RCNMV preferentially interferes with the accumulation of long small-interfering RNAs (24-26 nt) in an RNAi induced by a hairpin dsRNA. Collectively, we propose a model that for viral RNA replication, RCNMV deprives RNAi machinery of a factor, which is likely involved in Dicer-mediated dsRNA cleavage.
