TRIM13 Positively Regulates the NF-κB Signaling Pathway Induced by Encephalomyocarditis Virus.

Encephalomyocarditis virus (EMCV) belongs to the genus Cardiovirus of the family Picornaviridae. It is a non-enveloped, positive-sense, single-stranded RNA virus and an important pathogen causing encephalomyocarditis (EMC). Tripartite motif 13 (TRIM13) is a member of the tripartite motif (TRIM) family and serves as an important effector molecule in antiviral innate immunity. However, its antiviral activity and underlying molecular mechanisms during EMCV infection remain unknown. In this study, we identified TRIM13 as a regulator of NF-κB activation. TRIM13, dependent on its E3 ubiquitin ligase activity, directly binds to IκBα and dose-dependently increases its phosphorylation level. To determine the chain type of IκBα polyubiquitination, antibodies specific for K48-linked and K63-linked ubiquitin were used. Our data indicated that IκBα was subjected to polyubiquitination independent of K48 and K63 linkages. This interaction promotes non-K48/K63-linked polyubiquitination of IκBα, thereby inducing NF-κB nuclear translocation. Subsequently, nuclear NF-κB activates the secretion of pro-inflammatory cytokines, exacerbating inflammatory responses and ultimately facilitating EMCV infection.