The EBV BRLF1 Protein Has Sequence And Functional Similarity With The C-myb Oncogene

Abstract

It has recently been recognized that the Epstein-Barr virus (EBV) immediate-early (IE) gene product, BZLF1, plays a crucial role in disrupting iral latency (1). The BZLF1 (Z) protein is capable of binding to AP-1 sites as well as some sites unrelated to AP-1 (referred to as ZRE’s), and appears to function as a transcriptional transactivator through binding to these responsive promoter elements (2–5). However, it appears that the function of Z as a transactivator can be significantly affected by the host cell context. We have previously reported that the EBV early BMRF1 (EAD) promoter is efficiently transactivated by Z alone in epithelial cells such as HeLa, whereas Z has only a small effect on this promoter in lymphoid cell lines such as Jurkat(6). In addition, we have shown that this inefficient transactivation of the BMRF1 promoter by Z in lymphoid cells can be greatly increased by cotransfection with the EBV BRLF1 (R) IE gene product (a transcriptional transactivator in its own right), and have suggested that the combination of Z and R is required for maximal transactivation of certain promoters(6). In this report we demonstrate that the cellular c-myb proto-oncogene, like R, can cooperate synergistically with Z in lymphoid cells in activating the BMRF1 promoter.