CHARACTERIZATION OF 5'-UPSTREAM SEQUENCE OF THE LATENT MEMBRANE-PROTEIN-1 (LMP-1) GENE OF AN EPSTEIN-BARR-VIRUS IDENTIFIED IN NASOPHARYNGEAL CARCINOMA TISSUES

Sequence variations of the 5'-upstream region of latent membrane prote in 1 (LMP-1) in two Epstein-Barr virus (EBV) strains have been reporte d before (Chen et al., 1992). To investigate the effect of these varia tions on gene expression, we constructed a series of deletion plasmids encompassing positions -950 to +20 of the LMP-1 promoter region and t ested for the ability to drive chloramphenicol acetyltransferase (CAT) gene expression in C33A cells. Results showed that the promoter activ ities of constructs from NPC strain were 3-ford lower than the corresp onding constructs from the B95-8 strain. In addition, the region betwe en -54 and +20 contained the basic, constitutive promoter activity for both strains. Sequence analysis of this region indicated that an acti vating transcription factor (ATF) binding site, TGACGTAG, which is pre sent in B95-8 strain was changed to TCTCGTAG in NPC strain. A chimeric plasmid study suggested that these sequence variations in the ATF bin ding site may contribute to the 3-fold increase of CAT activity observ ed for B95-8 strain. Furthermore, the activity of the promoter constru cts was not activated by EBV-encoded nuclear antigen 2 (EBNA-2) in C33 A cells. However, the promoter activities were upregulated in B-lympho cyte cells such as CG3 and CA46 cells.