Influenza D virus Matrix protein 1 restricts the type I interferon response by degrading TRAF6

Influenza D virus (IDV) is an emerged virus that was first isolated in 2011 in the United States. Evidence suggests that IDV has broad host tropism and zoonotic potential. However, the immune evasion mechanism of IDV has not been explored. In the present study, we identified that the Matrix protein 1 (M1) of IDV is a negative regulator of virus- or RIG-IN-triggered type I interferon induction. Co-immunoprecipitation experiments revealed that M1 specifically interacts with tumor necrosis factor receptor associated factor 6 (TRAF6) and potentiates its proteasomal degradation by promoting K48-linked polyubiquitination. Moreover, we discovered that E3 ubiquitin ligase KEAP1 is recruited by M1 to catalyze K48-linked polyubiquitination of TRAF6, and promotes TRAF6 destabilization. Consequently, the degradation cascade mediated by M1 blocks RIG-I-TRAF6 mediated interferon signaling. Taken together, our findings reveal a negative regulatory role for the IDV M1 in the type І interferon pathway.