Plays a key role in the switch from latent infection to lytic cycle producing new virions. Acts as a transcription factor, inducing early lytic cycle genes, and as a origin binding protein for genome replication. BZLF1 activates the promoter of another EBV gene (BSLF2+BMLF1). Homodimer. Interacts with human UBN1, CRTC2 and RACK1. Interacts (via N-terminus) with human PAX5 (via N-terminus); this interaction inhibits BZLF1-mediated lytic viral reactivation. Belongs to the bZIP family.