SUMOylation-dependent degradation of nucleocapsid is responsible for <i>Pestivirus</i> uncoating

The fusion of the viral membrane and genome release are hallmark events of enveloped virus infections. However, the related dynamic mechanisms of most viruses remain poorly understood. Here, we demonstrate that VCP directly interacts with the CSFV core protein, and the core protein undergoes proteasomal degradation mediated by the PSMD2 and PSMB2 subunits, with VCP acting as a critical mediator. Surprisingly, this degradation process is independent of ubiquitination but exhibits a strong correlation with the SUMOylation of the nucleocapsid protein. In addition, we found that CSFV genome uncoating occurred in late endosomes, a process regulated by the host VCP. Depletion of VCP prevents viral trafficking to late endosomes and thereby disrupts uncoating efficiency. This is the first evidence implicating SUMOylation in viral uncoating. Deciphering the molecular intricacies governing viral uncoating is pivotal for propelling the development of broad-spectrum antiviral therapeutics aimed at the <i>Pestivirus</i> genus.