Participates in the expression of late viral mRNAs in part by interacting with ORF24 (PubMed:26468530, PubMed:25810551). Expressed before viral DNA replication, assembles at the viral pre-replication complexes (pre-RCs) and thus serves as a hub for recruiting a viral transcription complex to ORF24 to promote late viral gene expression (PubMed:28336944). Also plays a regulatory role in the viral life cycle by regulating host transcriptional regulators HIF1A and EPAS1 (PubMed:31189709). Interacts with ORF24; this interaction may serve as a core scaffold for the assembly of the viral transcription initiation complex (PubMed:26468530, PubMed:28336944). Interacts with ORF66 (PubMed:28336944, PubMed:31578296). Interacts with ORF18 (PubMed:28336944). Interacts with ORF23 (PubMed:28336944). Interacts with ORF31 (PubMed:28336944, PubMed:25810551). Interacts with host EPAS1; this interaction stabilizes host EPAS1, ensuring its transcriptional activity (PubMed:31189709). Recruited to nuclear replication compartments. Deletion results in reduced immediate early and early lytic gene expression and blocked late gene expression, while viral DNA replication seems not affected. Belongs to the herpesviridae UL95 family.