| EBNA1 (Epstein–Barr virus nuclear antigen 1) is the latent episome maintenance protein of Epstein–Barr virus and is expressed in every EBV-associated malignancy, where it anchors the circular viral genome to host chromatin and coordinates its replication and partitioning during host cell division while also modulating viral and cellular transcription. EBNA1 contains an N-terminal region with glycine–alanine repeats that limit its proteasomal processing, a central DNA-binding and dimerization domain that recognizes clustered EBNA1 sites within the viral origin of plasmid replication (oriP), and a C-terminal region that interacts with chromosomal tethering proteins; this modular organization allows EBNA1 dimers bound at oriP’s family of repeats to recruit the cellular replication machinery and ensures that EBV episomes are duplicated once per cell cycle and segregated to daughter nuclei in step with host chromosomes, providing the molecular basis for stable latent persistence without viral integration. EBNA1 binds both viral and cellular promoters and can act as a transcriptional regulator, altering expression of host genes involved in DNA damage responses, ubiquitin pathways, and cell survival. In Burkitt lymphoma models, EBNA1 is required for continued proliferation and survival of EBV-positive tumor cells, indicating that its activities support the malignant phenotype in addition to maintaining viral genomes. In nasopharyngeal carcinoma, EBNA1 is one of the few viral proteins consistently expressed, and EBNA1 expression correlates with disruption of PML nuclear bodies, changes in DNA damage signaling, and enhanced survival and growth of epithelial tumor cells, placing this protein at the center of EBV’s contribution to NPC biology. Interactions between EBNA1 and host regulatory axes that control p53 also emerge in EBV-positive B-cell lymphomas, where EBNA1 can influence expression of genes that inhibit p53 function and thereby weaken cell-cycle checkpoints and apoptotic responses, aligning EBNA1-mediated episome maintenance and transcriptional control with impaired tumor suppressor activity. EBNA1’s combination of oriP-specific DNA binding, chromatin tethering, and transcriptional modulation defines it as a multifunctional viral nuclear factor that sustains latent infection and shapes host gene expression programs, and its invariant presence in EBV-carrying tumor cells makes EBNA1 both a central mechanistic driver of EBV latency and an attractive target for therapeutic strategies aimed at destabilizing viral episomes or reversing EBV-dependent oncogenic signaling. |
