TRANSCRIPTION START SITES DOWNSTREAM OF THE EPSTEIN-BARR-VIRUS (EBV) FP PROMOTER IN EARLY-PASSAGE BURKITT-LYMPHOMA CELLS DEFINE A 4TH-PROMOTER FOR EXPRESSION OF THE EBV EBNA-1 PROTEIN

In Epstein-Barr virus (EBV)-transformed B lymphoblastoid and many Burk itt lymphoma cell lines, the EBV EBNA-1 protein is one of six viral nu clear antigens expressed from a common transcription unit under the co ntrol of one of two promoters, Wp or Cp. In contrast, EBNA-1 is the on ly EBV nuclear antigen expressed in Burkitt and other EBV-positive tum ors. We previously identified a promoter of EBNA-1 transcription, desi gnated Fp, in early-passage Mutu Burkitt tumor cells, and this promote r is also active in long-term Mutu and Akata Burkitt cell lines which maintain the exclusive expression of EBNA-1 characteristic of the tumo r, However, transcription initiation within Fp reporter gene plasmids in EBV-negative cells occurs at positions 100 to 200 bases downstream of the Fp start site in the BamHI-Q restriction fragment. Here we demo nstrate that transcription initiation within newly established Burkitt lymphoma cell lines is consistent with the transcription initiation w e observed in reporter plasmids. Furthermore, previous observations of transcription from Fp to generate EBNA-1 transcripts can be attribute d to lytic cycle gene expression. These data, in conjunction with our previous characterization of promoter regulatory elements, define a fo urth EBNA-1 promoter, Qp, that is active in latently infected Burkitt tumor cells.