Targeting PRMT7-mediated monomethylation of MAVS enhances antiviral innate immune responses and inhibits RNA virus replication.

RIG-I-like receptors (RLRs)-mitochondrial antiviral signaling protein (MAVS) are crucial for type I interferon (IFN) signaling pathway and innate immune responses triggered by RNA viruses. However, the regulatory molecular mechanisms underlying RNA virus-activated type I IFN signaling pathway remain incompletely understood. Here, we found that protein arginine methyltransferase 7 (PRMT7) serves as a negative regulator of the type I IFN signaling pathway by interacting with MAVS and catalyzing monomethylation of arginine 232 (R232me1) in MAVS. RNA virus infection leads to the downregulation and dissociation of PRMT7 from MAVS as well as the decrease of R232me1 methylation, enhancing MAVS/RIG-I interaction, MAVS aggregation, type I IFN signaling activation, and antiviral immune responses. Knock-in mice with MAVS R232 substituted with lysine (Mavs^R232K-KI) are more resistant to Vesicular Stomatitis Virus infection due to enhanced antiviral immune responses. PiPRMT7-MAVS, a short peptide inhibitor designed to interrupt the interaction between PRMT7 and MAVS, inhibits R232me1 methylation, thereby enhancing MAVS/RIG-I interaction, promoting MAVS aggregation, activating type I IFN signaling, and bolstering antiviral immune responses to suppress RNA virus replication. Moreover, the clinical relevance of PRMT7 is highlighted that it is significantly downregulated in RNA virus-infected clinical samples, such as blood samples from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Ebola virus, as well as H1N1-infected bronchial epithelial cells. Our findings uncovered that PRMT7-mediated arginine methylation plays critical roles in regulating MAVS-mediated antiviral innate immune responses, and targeting arginine methylation might represent a therapeutic avenue for treating RNA viral infection.