Impact of deubiquitination of Epstein-Barr virus Rta and Zta on lytic development

Rta and Zta are transcription factors expressed by Epstein-Barr virus (EBV) during the immediate-early stage of the lytic cycle. While these two proteins do not interact directly, they bind to a scaffold protein, RanBPM, to synergistically activate the transcription of EBV lytic genes. Earlier studies have shown that both Rta and Zta are destabilized through ubiquitination, which plays a crucial role in influencing EBV's lytic development. It is also known that Rta's ubiquitination is facilitated by the ubiquitin E3 ligase, RNF4. In this study, we show that RNF4 also promotes the ubiquitination of Zta. Meanwhile, a deubiquitinase, ubiquitin-specific protease (USP11), is known to interact with RanBPM. When tethered to RanBPM, Rta and Zta are deubiquitinated and stabilized by USP11. While host cells may utilize ubiquitination as a defense mechanism to destabilize Rta and Zta, thereby restricting EBV proliferation, EBV exploits RanBPM and the deubiquitination of Rta and Zta as a counter-defense strategy that favors EBV lytic replication. This study uncovers the interplay between the host and the viral mechanisms involving RNF4 and USP11 in modulating EBV lytic progression.IMPORTANCEEpstein-Barr virus (EBV) is known to express two crucial transcription factors, Rta and Zta, which are essential for activating the transcription of viral lytic genes. These two proteins are indispensable for viral lytic proliferation. While Rta and Zta can function independently to promote transcription, they also cooperate synergistically, leading to robust expression of EBV lytic proteins. In an earlier study, we showed that this synergy requires the formation of a complex involving Rta, Zta, and RanBPM at the Zta response elements in EBV lytic promoters. Recent studies showed that, despite their importance, these transcription factors are destabilized by ubiquitination, potentially serving as a mechanism through which the host restricts EBV proliferation. This study shows that EBV exploits USP11, which interacts with RanBPM, to deubiquitinate and stabilize Rta and Zta. The stabilization by USP11 is critical for EBV to overcome host-imposed restrictions and maximize its lytic proliferation.