TRIM33 promotes spring viremia of carp virus replication by degrading the antiviral protein viperin_sv1

TRIM33 is a member of the tripartite motif (TRIM) superfamily which contributes to regulate a multitude of cellular processes, including innate immune responses. Viperin_sv1 has recently been identified as a novel splice variant of viperin that triggers a strong antiviral effect by activating the interferon signaling pathway. SVCV infection is known to cause the degradation of viperin_sv1 through a proteasome pathway; however, the underlying mechanism remains unsolved. In this study, we identify that TRIM33 protein interacts and colocalizes with viperin_sv1 protein to induce its degradation. Additional analysis revealed that the N-terminus, but not the C-terminus, region of TRIM33 is essential for interacting with and inducing the degradation of viperin_sv1 protein. Moreover, SVCV infection enhances the expression of TRIM33 which is proved to reduce the type-1 interferon response and to promote viral replication. In conclusion, our study demonstrates that TRIM33 enhances the replication of SVCV by dampening the antiviral protein viperin_sv1 expression. These findings may lay a foundation for developing novel therapeutic strategies to halt SVCV infection.