Description
EBNA1 is the only EBV protein consistently expressed in all proliferating infected cells and plays several important roles in EBV latent infection, including the initiation of EBV DNA replication, the mitotic segregation of the EBV genomes, and transcriptional activation of other EBV latency proteins. several pieces of evidence suggest that EBNA1 plays a direct role in cellular transformation by EBV. First, EBNA1 is expressed in all EBV-associated tumors and is the only viral protein expressed in some of these tumors. Second, transgenic mice expressing EBNA1 develop malignant B cell lymphomas. Third, the expression of EBNA1 in Hodgkin cells enhances their ability to form tumors in nonobese diabetic-SCID mice. Fourth, EBV genomes lacking the EBNA1 gene are several thousand-fold less efficient at B cell immortalization than EBV genomes expressing EBNA1. Fifth, interference with EBNA1 function in Burkitt's lymphoma cells by overexpression of the EBNA1 DNA binding domain increased cell death, suggesting that EBNA1 normally provides a survival function for these cells