DTX3L Enhances Type I Interferon Antiviral Response by Promoting the Ubiquitination and Phosphorylation of TBK1

Studies already revealed that some E3 ubiquitin ligases participated in the immune response after viral infection by regulating the type I interferon (IFN) pathway. Here, we demonstrated that type I interferon signaling enhanced the translocation of ETS1 to the nucleus and the promoter activity of E3 ubiquitin ligase DTX3L (deltex E3 ubiquitin ligase 3L) after virus infection and thus increased the expression of DTX3L. Further experiments suggested that DTX3L ubiquitinated TBK1 at K30 and K401 sites on K63-linked ubiquitination pathway. DTX3L was also necessary for mediating the phosphorylation of TBK1 through binding with the tyrosine kinase SRC: both together enhanced the activation of TBK1. Therefore, DTX3L, being an important positive-feedback regulator of type I interferon, exerted a key role in antiviral response. IMPORTANCE Our present study evaluated DTX3L as an antiviral molecule by promoting IFN production and establishing an IFN-β-ETS1-DTX3L-TBK1 positive-feedback loop as a novel immunomodulatory step to enhance interferon signaling and inhibit respiratory syncytial virus (RSV) infection. Our finding enriches and complements the biological function of DTX3L and provides a new strategy to protect against lung diseases such as bronchiolitis and pneumonia that develop with RSV.