ASFV pD345L protein negatively regulates NF-kB signaling through inhibiting IKK kinase activity

The NF-{kappa}B pathway is an essential signaling process against viral infection including African swine fever virus (ASFV). ASFV encodes for more than 151 proteins by its own transcription machinery and possesses a great capacity to evade or subvert antiviral innate immune responses. A couple of such viral proteins have been reported, but many remain unknown. Here, we showed that pD345L, an ASFV-encoded lambda-like exonuclease, is an inhibitor of cGAS/STING mediated NF-{kappa}B sig-naling by blocking IKK/{beta} kinase activity. Specifically, we showed that overexpression of pD345L suppresses cGAS/STING induced IFN{beta} and NF-{kappa}B activation, resulting in decreased transcription of IFN{beta} and several pro-inflammatory cytokines, including IL-1, IL-6, IL-8, and TNF. In addition, we showed that pD345L targeted at or downstream of IKK and upstream of p65. Importantly, we found that pD345L associates with KD and HLH domains of IKK and LZ domain of IKK{beta}, and thus interrupts their kinase activity on downstream substrate I{kappa}B. Finally, we showed that pD345L inhibition of NF-{kappa}B signaling was independent of its exonuclease activity. Taken together, we concluded that pD345L blocks IKK/{beta} kinase activity by protein-protein interaction and thus disrupts cGAS/STING mediated NF-{kappa}B signaling.