A20 is a negative regulator of IFN regulatory factor 3 signaling

IFN regulatory factor 3 (IR-F-3) is a critical transcription factor that regulates an establishment of innate immune status following detection of viral pathogens. Recent studies have revealed that two IkappaB kinase (IKK)-like kinases. NT-kappaB-activating kinase/Traf family member-associated NF-kappaB activator-binding kinase 1 and IKK-i/IKKepsilon. are responsible for activation of IRF-3. but the regulatory mechanism of the IRF-3 signaling pathway has not been fully understood. In this study, we report that IRF-3 activation is suppressed by A20, which was initially identified as an inhibitor of apoptosis and inducibly expressed by dsRNA. A-30 physically interacts with NF-kappaB -activating kinase/Traf family member-associated NF-kappaB activator-binding kinase I and IKK-iKKepsilon. and inhibits dimerization of IRF-3 following engagement of TLR3 by dsRNA or Newcastle disease virus infection, leading to suppression of the IFN stimulation response element- and IFN-beta promoter-dependent transcription. Importantly, knocking down of A20 expression by RNA interference results in enhanced IRF-3-dependent transcription triggered by the stimulation of TLR3 or virus infection. Our study thus demonstrates that A20 is a candidate negative regulator of the signaling cascade to IRF-3 activation in the innate antiviral response.