THE EPSTEIN-BARR-VIRUS EBNA-1 PROMOTER QP REQUIRES AN INITIATOR-LIKE ELEMENT

Expression of the Epstein-Barr virus (EBV) EBNA-1 protein within EBV-p ositive tumor cells and subpopulations of latently infected B lymphocy tes in vivo is mediated by the promoter Qp. Previous studies have esta blished that Qp is a TATA-less promoter whose activation requires only proximal regulatory elements and that it is negatively autoregulated through two EBNA-1 binding sites downstream of the transcription initi ation sites. The objective of this study was to better define the prop erties of an essential positive regulatory element (QRE-2) adjacent to a major transcription start site of Qp and to evaluate the contributi ons of other potential regulatory elements proximal to the Qp start si te. Using DNA affinity purification and UV cross-linking, we have iden tified the QRE-2-binding protein as a single polypeptide of similar to 40 kDa., The DNA-binding properties of this protein are clearly disti nct from those of the TATA-binding protein, suggesting that in the abs ence of a TATA box, QRE-2 may function as an initiator element to dire ct assembly of TFIID near the transcription start site. ?Mutational an alysis of potential regulatory elements, furthermore, indicated that t he putative E2F binding sites within the EBNA-1 binding domain can exe rt a positive influence on Qp that is EBNA-1 independent, suggesting t hat these regulatory elements play. an additional if not different rol e in Qp regulation than previously proposed. A model for the regulatio n of Qp consistent with the current and previous findings which provid es for a simple but efficient mechanism of ensuring the EBNA-1 express ion necessary to sustain long-term latency is presented.