Antiviral RNA interference responses induced by XXXX infection of mosquito cells: characterization, origin, and frequency-dependent functions of virus-derived small interfering RNAs.

@entity4224 @entity3598 @entity197 @entity3597 @entity34183
RNA interference (RNAi) is an important mosquito defense mechanism against @entity34183 . In this paper we study the processes underlying antiviral RNAi in @entity197 -derived U4.4 mosquito cells infected with @entity3597 ( @entity3598 ) (Togaviridae; Alphavirus). The production of virus-derived small interfering RNAs (viRNAs) from viral double-stranded RNA (dsRNA) is a key event in this host response. dsRNA could be formed by RNA replication intermediates, by secondary structures in RNA genomes or antigenomes, or by both. Which of these dsRNAs is the substrate for the generation of viRNAs is a fundamental question. Here we used deep sequencing of viRNAs and bioinformatic analysis of RNA secondary structures to gain insights into the characteristics and origins of viRNAs. An asymmetric distribution of @entity3598 -derived viRNAs with notable areas of high-level viRNA production (hot spots) and no or a low frequency of viRNA production (cold spots) along the length of the viral genome with a slight bias toward the production of genome-derived viRNAs over antigenome-derived viRNAs was observed. Bioinformatic analysis suggests that hot spots of viRNA production are rarely but not generally associated with putative secondary structures in the @entity3598 genome, suggesting that most viRNAs are derived from replicative dsRNA. A pattern of viRNAs almost identical to those of A. albopictus cells was observed for @entity4224 -derived Aag2 cells, suggesting common mechanisms that lead to viRNA production. Hot-spot viRNAs were found to be significantly less efficient at mediating antiviral RNAi than cold-spot viRNAs, pointing toward a nucleic acid-based viral decoy mechanism to evade the RNAi response.
