Host OTUB2 and viral plpro stabilize NSP8 to promote SARS-CoV-2 replication

The ubiquitin-proteasome system (UPS) plays a central role in antiviral defense but is also frequently hijacked by viruses to facilitate their replication. Here, we demonstrate that the host deubiquitinase OTUB2 stabilizes the viral replication factor NSP8 of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) through a dual-track mechanism. OTUB2 directly removes polyubiquitin chains from NSP8 to prevent its degradation. In parallel, OTUB2 stabilizes the viral papain-like protease (PLpro), which further promotes NSP8 stability through deubiquitination. Together, these effects preserve the functional integrity of the viral replication-transcription complex. Mechanistically, OTUB2-mediated stabilization of NSP8 potentiates NSP8-dependent suppression of type I interferon signaling, thereby promoting viral replication and immune evasion. Importantly, inhibition of OTUB2 disrupts OTUB2-mediated stabilization of NSP8 and PLpro, resulting in a marked reduction in viral replication and disease severity in cell culture systems and a hamster infection model. Collectively, our findings reveal a previously unrecognized mechanism by which SARS-CoV-2 utilizes the host deubiquitination system to stabilize its replication machinery and identify OTUB2 as a potential target for host-directed antiviral intervention.