RIG-I and MDA-5 detection of viral RNA-dependent RNA polymerase activity restricts positive-strand RNA virus replication.

ABSTRACT: Type I interferons (IFN) are important for antiviral responses. Melanoma differentiation-associated gene 5 (MDA-5) and retinoic acid-induced gene I (RIG-I) proteins detect cytosolic double-stranded RNA (dsRNA) or 5'-triphosphate (5'-ppp) RNA and mediate IFN production. Cytosolic 5'-ppp RNA and dsRNA are generated during viral RNA replication and transcription by viral RNA replicases [RNA-dependent RNA polymerases (RdRp)]. Here, we show that the Semliki Forest virus (SFV) RNA replicase can induce IFN-? independently of viral RNA replication and transcription. The SFV replicase converts host cell RNA into 5'-ppp dsRNA and induces IFN-? through the RIG-I and MDA-5 pathways. Inactivation of the SFV replicase RdRp activity prevents IFN-? induction. These IFN-inducing modified host cell RNAs are abundantly produced during both wild-type SFV and its non-pathogenic mutant infection. Furthermore, in contrast to the wild-type SFV replicase a non-pathogenic mutant replicase triggers increased IFN-? production, which leads to a shutdown of virus replication. These results suggest that host cells can restrict RNA virus replication by detecting the products of unspecific viral replicase RdRp activity.

SUBMITTER: Nikonov A 

PROVIDER: S-EPMC3764220 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature