NSP7 Molecular Degrader Attenuates Coronaviral Infection Through the β-TrCP1/FBXO5 Axis.

NSP7 (Non-Structural Protein 7) of SARS-CoV-2 is a crucial component for viral replication and transcription. In this study, it is revealed that the host E3 ubiquitin ligase FBXO5 suppresses viral replication by mediating NSP7 lysine-48-linked ubiquitination and subsequent proteasomal degradation. Interestingly, it is also determined that NSP7 expression impairs the host antiviral response by inhibiting the ISGylation of melanoma differentiation-associated protein 5 (MDA5), a key sensor for viral RNA. Through an unbiased esiRNA screen, it is identified that NSP7 ubiquitination is coregulated by β-TrCP1 and the kinase TAF1. Additionally, this study uncovers a small molecule FBXO5 stabilizer that disrupts the β-TrCP1-FBXO5 interaction, thereby markedly enhancing NSP7 degradation and effectively mitigating SARS-CoV-2 infection. Taken together, the findings reveal a novel mechanism for NSP7 regulation and suggest that small-molecule activators of the E3 ubiquitin ligase FBXO5 represent a promising new class of host-directed antiviral therapies.