Regulation of Interferon Regulatory Factor 3-Dependent Innate Immunity by the HCV NS3/4A Protease

Interferon regulatory factor 3 (IRF-3) is a ubiquitously expressed latent cellular transcription factor that plays a pivotal role in control of innate, type I interferon (IFN) antiviral responses. After viral infections, IRF-3 is activated by specific C-terminal phosphorylation, which induces its dimerization and nuclear translocation, whereupon IRF-3 activates the transcription of type I IFNs and a number of other antiviral effector genes. Many viruses have evolved strategies that antagonize signaling mechanisms leading to IRF-3 activation. Recent studies have shown that hepatitis C virus blocks IRF-3 activation and subsequent IFN induction by cleaving critical cellular substrates within the intracellular antiviral signaling pathways upstream of IRF-3 with its major protease, NS3/4A.