USP39 promotes antiviral defense through post-transcriptional control of RIG-I and stabilization of STING

RIG-I and STING are critical for mediating the RIG-I and cGAS-STING signaling pathways that guard against viral infection. Here, we report that ubiquitin-specific peptidase 39 (USP39) positively regulates the RIG-I and cGAS-STING pathways to induce antiviral innate immunity in vitro and in vivo. The USP39 deficiency impaired the antiviral immune response of macrophages, leading to low type I IFNs expression, and high RNA and (e.g., VSV, H1N1 PR8) DNA virus (e.g., HSV-1) replication. Moreover, USP39-deficient mice were more sensitive to VSV or HSV-1 infection than control mice. Conversely, USP39 overexpression promoted the antiviral immune response. Mechanistically, we found that USP39 regulates RIG-I protein expression by promoting pre-RIG-I mRNA splicing and maturation. In addition, we also revealed that USP39 interacts with and stabilizes STING protein by deubiquitinating K48-linked polyubiquitin of STING at K288. These data show that USP39 positively regulates RNA and DNA-virus-induced RIG-I and cGAS-STING signaling, respectively, by promoting post-transcriptional control of RIG-I and stabilization of STING. These data provide new insights and potential therapeutic targets to control viral infections.