Immediate early (EI) protein that plays many roles during productive infection including regulation of host cell cycle progression, regulation of viral gene expression or nuclear export of intronless viral RNAs. Acts as a transcriptional transactivator via interaction with the cellular transcription elongation factor SUPT6H (PubMed:22171252). In addition, acts as a post-transcriptional transactivator that mediates the nuclear export of unspliced mRNAs via interaction with DDX39B, a component of the cellular mRNA export machinery (PubMed:16478985, PubMed:26178996). Self-associates and forms a tetramer (PubMed:29921674). Interacts with host DDX39A and DDX39B; these interactions are required for UL69 function in mRNA export (PubMed:26178996). Interacts with host SUPT6H (PubMed:22171252). Interacts with host EIF4A1 and PABPC1 (PubMed:20133758). Interacts with host PRMT6. Shuttles between host nucleus and cytoplasm. Phosphorylated by UL97 and host CDK1, CDK7 and CD9. Phosphorylation by CDKs impacts on UL69 nuclear localization and activity (By similarity). Arginine methylated via N-terminal arginine motif. Belongs to the HHV-1 ICP27 protein family.