RNF31 restricts EV-A71 replication through innate immune activation and VP4 degradation, and is antagonized by viral 3C proteases

A persistent evolutionary arms race exists between enteroviruses and their hosts, in which viruses employ multiple strategies to antagonize host antiviral defenses and sustain efficient replication. However, how host restriction factors are broadly targeted by enteroviruses during this process, as well as the underlying molecular mechanisms, remain poorly understood. Here, we identify Ring Finger Protein 31 (RNF31) as a previously unrecognized host restriction factor that limits enterovirus A71 (EV-A71) replication through a dual antiviral mechanism. Specifically, RNF31 enhances innate antiviral immune signaling by promoting K63-linked polyubiquitination of Retinoic acid-inducible gene I (RIG-I). Simultaneously, RNF31 directly suppresses EV-A71 replication by inducing K27- and K48-linked polyubiquitination of the Viral Protein 4 (VP4), thereby facilitating its proteasome-dependent degradation. Furthermore, we demonstrate that the viral 3C protease (3Cpro) cleaves RNF31 at residue Q400, abolishing both RNF31-mediated activation of innate immunity and VP4 degradation, ultimately resulting in the loss of its antiviral activity. Notably, 3Cpro from multiple enteroviruses, including Coxsackievirus A16 (CV-A16), Coxsackievirus B3 (CV-B3), and Enterovirus D68 (EV-D68), cleave RNF31 at this same conserved site. Consistent with these findings, RNF31 significantly inhibits the replication of these diverse enteroviruses. Collectively, this study establishes RNF31 as a host restriction factor that suppresses the replication of multiple enteroviruses and reveals a shared immune evasion strategy employed by enteroviruses.