REDEFINING THE EPSTEIN-BARR VIRUS-ENCODED NUCLEAR ANTIGEN EBNA-1 GENEPROMOTER AND TRANSCRIPTION INITIATION SITE IN GROUP-I BURKITT-LYMPHOMA CELL-LINES

The Epstein-Barr virus-encoded nuclear antigen EBNA-1 gene promoter fo r the restricted Epstein-Barr virus (EBV) latency program operating in group I Burkitt lymphoma (BL) cell lines was previously identified in correctly. Here we present evidence from RACE (rapid amplification of cDNA ends) cloning, reverse transcription-PCR, and S1 nuclease analyse s, which demonstrates that the EBNA-1 gene promoter in group I BL cell lines is located in the viral BamHI Q fragment, immediately upstream of two low-affinity EBNA-1 binding sites. Transcripts initiated from t his promoter, referred to as Qp, have the previously reported Q/U/K ex on splicing pattern. Qp is active in group I BL cell lines but not in group III BL cell lines or in EBV immortalized B-lymphoblastoid cell l ines. In addition, transient transfection of Qp-driven reporter constr ucts into both an EBV-negative BL cell line and a group I BL cell line gave rise to correctly initiated transcripts. Inspection of Qp reveal ed that it is a TATA-less promoter whose architecture is similar to th e promoters of housekeeping genes, suggesting that Qp may be a default promoter which ensures EBNA-1 expression in cells that cannot run the full viral latency program. Elucidation of the genetic mechanism resp onsible for the EBNA-1-restricted program of EBV latency is an essenti al step in understanding control of viral latency in EBV-associated tu mors.