Transcription of BamHI-A region of the EBV genome in NPC tissues and B cells.

Analysis by Northern blotting and sequencing of cDNA clones from a transcription library of a tumor biopsy from a nasopharyngeal carcinoma (NPC) patient showed that the BamHI-A region of the Epstein-Barr virus genome is abundantly and regularly transcribed in tumor tissues from NPC patients. The transcription occurred in a rightward direction terminating between coordinates 160,965 and 160,995, where two polyadenylation sites are located. Rightward transcription of this region also occurred in B lymphoid cells harboring the viral genome, albeit at a lower level than in the tumor tissues. Differential splicing yields a family of related transcripts displaying at least four splicing patterns. Different promoters may be utilized, further contributing to the diversity of this family of transcripts. A 2.8-kb unspliced transcript present in B95-8 cells was probably initiated from a TATA box located in position 158,204, while the other transcripts may utilize other promoters localized to other regions. All the transcripts encompass a putative open reading frame, BARFO, which is predicted to encode a basic protein of about 20 kDa. It shares 40% colinear amino acid sequence homology with the DNA binding region of a transcription factor, ICP4, specified by herpes simplex virus.