EBNA1 is the latent origin binding protein of Epstein-Barr virus and the only viral protein needed for the replication and stable persistence of EBV episomes. The contributions of EBNA1 include facilitating the initiation of DNA synthesis and ensuring the even distribution of the viral episomes to daughter cells during mitosis, a function that involves tethering the episomes to the cellular chromosomes. EBNA1 also activates the transcription of other viral latency genes important for cell immortalization and can autoregulate its own expression. In addition, EBNA1 has been found to alter the cellular environment in a number of ways consistent with a direct contribution to cell immortalization and malignant transformation.
from Epstein-Barr Virus: Latency and TransformationFurther reading: