B cell terminal differentiation factor XBP-1 induces reactivation of Kaposi's sarcoma-associated herpesvirus.

The herpesvirus life cycle has two distinct phases: latency and lytic replication. The viral immediate early protein replication and transcription activator (RTA) plays a central role in mediating the balance between these two phases. Here, we demonstrate that a B cell terminal differentiation factor X-box binding protein 1 (XBP-1) can effectively initiates Kaposi's sarcoma-associated herpesvirus (KSHV) reactivation by activating the RTA promoter, which results in the induction of other viral lytic transcripts. We also showed splicing of the XBP-1 mRNA which specifically occurs during B cell differentiation is critical in triggering KSHV reactivation. This work demonstrates the integration of KSHV reactivation mechanisms with host cell differentiation.