TANK potentiates antiviral innate immunity by recruiting deubiquitinase USP46 to activate IKKε.

IKKε plays an important role in interferon (IFN) production, however, its regulation remains poorly understood. In this study, we demonstrate that black carp TANK (bcTANK) interacts with bcIKKε and significantly enhances its activation of bcIRF3 and bcIRF7, leading to the improved antiviral activity against spring viremia of carp virus (SVCV). Mechanistically, bcTANK recruits deubiquitinase bcUSP46 to bcIKKε and leads to a reduction in polyubiquitination of and a concurrent increase in phosphorylation of bcIKKε, which suggests the activation status of this molecule. Site-directed mutagenesis revealed that lysine residues K418 and K545 of bcIKKε are critical for bcIKKε-mediated IFN production. Furthermore, we identified the SVCV phosphoprotein (P) as a viral antagonist of bcTANK/bcIKKε/bcIRF cascade. The SVCV P protein interacts with bcIKKε, promotes its polyubiquitination, attenuates its phosphorylation and disrupts its interaction with bcTANK, bcUSP46, bcIRF3, and bcIRF7, thereby facilitating viral replication. Thus, our findings reveal a novel positive regulation of IKKε by TANK.