The C-Terminal Effector Domain of Non-Structural Protein 1 of Influenza A Virus Blocks IFN-ß Production by Targeting TNF Receptor-Associated Factor 3

Qian, Wei; Wei, Xiaoqin; Guo, Kelei; Li, Yongtao; Lin, Xian; Zou, Zhong; Zhou, Hongbo; Jin, Meilin

As reported previously, IKKε is recruited to the C-terminal region of MAVS following Sev or VSV infection, mediated by Lys63-linked polyubiquitination of MAVS at Lys500, resulting in the inhibition of downstream IFN signaling (31, 32) . Therefore, it was necessary to test whether wtNS1 or NS1/126-225 affect this process to accomplish its negative regulatory role in IFN-β production after Sev infection. The interaction of MAVS and IKKε was readily detected by Co-IP, while Sev infection resulted in a significant decrease in the MAVS-IKKε interaction. Interestingly, the interaction of MAVS and IKKε was remarkably increased when cotransfected with NS1/126-225 or wtNS1 (Figure 7E) , indicating that NS1/126-225 or NS1 promotes the recruitment of IKKε to MAVS. Furthermore, we measured the secretion of IFN-β in cell supernatants. Results showed that NS1/126-225 or NS1 inhibited the production of IFN-β mediated by MAVS-TRAF3 or MAVS-IKKε (Figure 7F) , implying that NS1/126-225 functions in downregulating IFN expression. Taken together, these results indicate that the association of the MAVS-TRAF3 complex is disrupted by NS1/126-225, which, in turn, blocks IFN-β production.