Deubiquitinase USP8 inhibits HIV-1 replication by suppressing Tat-mediated viral transactivation

Ubiquitin-specific proteases (USPs) modulate diverse virus-host interaction events through deubiquitination; thus, investigating their functional roles and molecular targets facilitates the interpretation of viral pathogenic mechanisms and informs the design of anti-virus strategies. The deubiquitinase USP8 has been reported to antagonize HIV-1 replication by reversing Vif-mediated ubiquitination of the host restriction factor A3G and shielding it from proteasomal degradation. Here, we identify an additional A3G-independent anti-HIV mechanism of USP8. In A3G-negative cells, USP8 exerts a potent inhibitory effect on HIV-1 replication by significantly suppressing viral transcription. Mechanistically, USP8 interacts with the HIV-1 trans-activator Tat through its C-terminal domain and mediates the removal of Tat’s polyubiquitination chains in a manner dependent on USP8 catalytic activity. This disrupts the association between Tat and the HIV-1 LTR transactivation response (TAR) element, thus impairing Tat-mediated viral transactivation. Furthermore, given the essential role of Tat in driving viral gene expression, silencing of USP8 triggers latent HIV-1 reactivation. Collectively, our results, along with previous work, reveal that USP8 acts as a compelling anti-HIV factor that, by regulating both host and viral proteins, ultimately suppresses HIV-1 replication. These results deepen our understanding of USP8-mediated HIV-1 restriction and provide insights for the development of novel anti-HIV therapeutic strategies.