Type I interferons are broadly used for antiviral therapy in clinical. However, the IFNs-mediated antiviral efficacy is commonly restricted by negative regulators. Here, we show that the ubiquitin-specific protease 5 (USP5) inhibits the IFNs-induced p-STAT1 activation (phosphorylation at tyrosine site of STAT1) and its downstream antiviral genes expression. We clarify that USP5 physically interacts with SMURF1 (Smad ubiquitination regulating factor 1) and IFNs signaling regulates the interaction and turnover of both proteins. USP5 enhances the stability and turnover of SMURF1 via decreasing its polyubiquitin expression level, which caused STAT1 to decrease. Importantly, USP5 is also involved in the SMURF1-mediated antiviral response, and its small-molecule inhibitor PYR41 remarkably enhances the IFNs antiviral efficacy. These findings reveal a previously unrecognized function of the USP5 and USP5-SMURF1 axis in regulating the IFNs-mediated antiviral activity.

I型干扰素在临床上广泛用于抗病毒治疗。但是，IFNs介导的抗病毒功效通常受到负调节剂的限制。在这里，我们显示泛素特异性蛋白酶5（USP5）抑制IFNs诱导的p-STAT1激活（STAT1酪氨酸位点的磷酸化）及其下游抗病毒基因表达。我们阐明，USP5与SMURF1（Smad泛素调节因子1）发生物理相互作用，而IFNs信号传导则调节两种蛋白的相互作用和更新。USP5通过降低SMURF1的多聚泛素表达水平来增强SMURF1的稳定性和周转率，从而导致STAT1降低。重要的是，USP5也参与SMURF1介导的抗病毒反应，其小分子抑制剂PYR41显着增强了IFNs的抗病毒功效。