EBNA-5, AN EPSTEIN-BARR VIRUS-ENCODED NUCLEAR ANTIGEN, BINDS TO THE RETINOBLASTOMA AND P53 PROTEINS

Epstein-Barr virus (EBV) immortalized human lymphoblastoid cell lines express six virally encoded nuclear proteins, designated EBV nuclear a ntigens 1-6 (EBNA-1-6). We show that the EBNA-5 protein (alternatively designated EBNA-LP) that is required for B-cell transformation can fo rm a molecular complex with the retinoblastoma (RB) and p53 tumor supp ressor proteins. Using EBNA-5 deletion mutants, we have found that a 6 6-amino acid-long peptide, encoded by the W repeat of the EBV genome, is sufficient for binding. Point mutations of RB and p53 that inhibit their complexing with other DNA viral oncoproteins do not affect their binding to EBNA-5. p53 competes with RB for EBNA-5 binding. Our data suggest that the mechanisms involved in EBV transformation may include impairment of RB and p53 function.