THE EPSTEIN-BARR-VIRUS DETERMINED NUCLEAR ANTIGENS EBNA-3A, EBNA-3B, AND EBNA-3C REPRESS EBNA-2-MEDIATED TRANSACTIVATION OF THE VIRAL TERMINAL PROTEIN-1 GENE PROMOTER

The Epstein-Barr Virus (EBV) nuclear antigen 2 (EBNA-2) has been shown to transactivate both cellular and viral gene promoters including the promoter for the viral terminal protein 1 gene (TP-1). We investigate d whether three other EBV nuclear antigens EBNA-3A, -3B, and -3C (whic h themselves share a degree of primary sequence homology) could also p lay a role in TP-1 gene regulation. The TP-1 promoter sequence was lin ked to the chloramphenicol acetyltransferase (CAT) gene and used in co transfection experiments in an EBV negative cell line with various com binations of vectors expressing individual EBNA-3s. In the absence of other EBV proteins, the EBNA-3s did not stimulate TP-1 promoter activi ty. In the presence of EBNA-2, the EBNA-3s were shown to be capable of reducing the level of TP-1 promoter-driven CAT activity. The EBNA-3s had no effect on a panel of heterologous promoters, indicating that EB NA-2 and/or transcription elements specific to the TP-1 promoter are e ssential for the observed activity of the EBNA-3s. The functional anta gonism between the EBNA-2 and EBNA-3 proteins may be important in the overall viral strategy. (C) 1994 Academic Press, Inc.