The USP43/RNF2 axis negatively regulates antiviral innate immunity by promoting TBK1 ubiquitination and degradation.

The E3 ubiquitin ligase usually regulates the substrate proteins ubiquitination and degradation, but the study of itself post-translational modification and stability is still elusive. Here, we reveal that E3 ubiquitin ligase ring finger protein 2 (RNF2) is deubiquitinated and stabilized by ubiquitin specific peptidase 43 (USP43) through interactome and quantitative ubiquitinome mass spectrometry analysis. This study demonstrated that USP43, as a deubiquitinating enzyme, negatively regulates the expression of type I interferon (IFN) and the Usp43 deficient enhances antiviral innate immune response against VSV infection both in vitro and in vivo. Mechanistically, USP43 negatively regulates antiviral immunity by promoting RNF2-mediated TBK1 ubiquitination and degradation. USP43 stabilizes RNF2 by removing K48-linked ubiquitination of RNF2 at Lys239 and Lys249, while RNF2 promotes TBK1 degradation by increasing K48-linked ubiquitination of TBK1 at Lys670. These findings uncover the E3 ubiquitin ligase RNF2 post-translational ubiquitination modification and stability regulation, and reveals a novel mechanism that the USP43/RNF2 axis in regulating antiviral innate immunity.