TBK1-METTL3 axis facilitates antiviral immunity.

mRNA mA modification is heavily involved in modulation of immune responses. However, its function in antiviral immunity is controversial, and how immune responses regulate mA modification remains elusive. We here find TBK1, a key kinase of antiviral pathways, phosphorylates the core mA methyltransferase METTL3 at serine 67. The phosphorylated METTL3 interacts with the translational complex, which is required for enhancing protein translation, thus facilitating antiviral responses. TBK1 also promotes METTL3 activation and mA modification to stabilize IRF3 mRNA. Type I interferon (IFN) induction is severely impaired in METTL3-deficient cells. Mettl3-lyz2-Cre mice are more susceptible to influenza A virus (IAV)-induced lethality than control mice. Consistently, Ythdf1 mice show higher mortality than wild-type mice due to decreased IRF3 expression and subsequently attenuated IFN production. Together, we demonstrate that innate signals activate METTL3 via TBK1, and METTL3-mediated mA modification secures antiviral immunity by promoting mRNA stability and protein translation.