EBV nuclear antigen 1 hijacks DDX5/BZLF1 axis to facilitate viral lytic replication.

Epstein-Barr virus (EBV) lytic replication is a key driver of viral dissemination and tumorigenicity in epithelial malignancies, such as nasopharyngeal carcinoma (NPC) and gastric cancer (GC). However, the underlying molecular mechanism and effective therapeutic strategy remain largely unknown. Here, we analyzed the EBV nuclear antigen 1 (EBNA1) interactome and identified DEAD-box helicase 5 (DDX5) as its novel partner. The N-terminal region (amino acids 1-88) of EBNA1 and the C-terminal domain of DDX5 were crucial for their binding. EBNA1 stabilized the DDX5 protein by impeding its proteasomal degradation via K48-linked polyubiquitin. EBNA1 facilitated EBV lytic replication in a DDX5-dependent manner. Furthermore, DDX5 bound to the promoter of BZLF1, which is the key switch of EBV reactivation, thus transactivating BZLF1 to drive viral lytic replication. Moreover, the small molecule inhibitor FL118 was able to disrupt this process by promoting DDX5 degradation, unveiling FL118 as a new potential antiviral drug. Our findings established a new functional axis of EBNA1/DDX5/BZLF1, adding to the knowledge about the role of EBNA1 in the regulation of EBV life cycle, particularly for lytic replication. The study also provided potential therapeutic strategy for EBV-associated epithelial tumors.