Figure 3.

Sensing of viral nucleic acids by DExD/H box helicases in drosophila and mammals. dsRNA is detected by Dicer-2 and RLRs (RIG-I and MDA5) in flies and mammals, respectively. These molecules contain phylogenetically related DExD/H box helicase domains, which mediate a conformational change in response to interaction with viral RNAs (dsRNA or single stranded RNA with a 5′ triphosphate extremity in the case of RIG-I). In drosophila (left panel), Dicer-2 processes dsRNA into siRNAs, and triggers an unidentified signal that leads to the inducible expression of the gene Vago, which controls the viral load in the fat body of infected flies. In mammals (right panel), RLRs activate the signal transducer IPS-1 and transcription factors of the IRF family, leading to production of interferons.