Epstein-Barr virus (EBV) nuclear antigen (EBNA) 2 (EBNA2) is involved in upregulating theEpstein-Barr virus (EBV) infection of resting human B lymphocytes results in the differentiation of infected B cells into lymphoblastoid cell lines (LCLs), which can be passaged indefinitely. These LCLs have an activated B-cell phenotype and express a subset of viral genes which are crucial for the transformation of the cells. The viral genes known to be critical for transformation are EBV nuclear antigens (EBNAs) 1, 2, 3A, and 3C and latency-associated membrane protein 1 (4,8,9,11,20).Expression of the EBNAs in LCLs is driven by the BamHI C promoter (Cp) and the BamHI W promoter (Wp) (Fig.