The activity of the Epstein-Barr virus BamHI W promoter in B cells is dependent on the binding of CREB/ATF factors

The programme of Epstein-Barr virus (EBV) gene expression that leads to vir us-induced growth transformation of resting B lymphocytes is initiated thro ugh activation of the BamHI W promoter, Wp, The factors regulating Wp, and the basis of its preferential activity in B cells, remain poorly understood . Previous work has identified a B cell-specific enhancer region which is c ritical for Wp function and which contains three binding sites for cellular factors. Here we focus on one of these sites and show, using bandshift ass ays, that it interacts with three members of the CREB/ATF family of cell tr anscription factors, CREB1,ATF1 and ATFa. A mutation which abrogates the bi nding of these factors reduces Wp reporter activity specifically in B cell lines, whereas a mutation which converts the site to a consensus CREB-bindi ng sequence maintains wild-type promoter function. Furthermore Wp activity in B cell, but not in non-B cell, lines could be inhibited by cotransfectio n of expression plasmids expressing dominant negative forms of CREB1 and AT F1, Increasing the basal activity of CREB/ATF proteins in cells by treatmen t with protein kinase A or protein kinase C agonists led to small increases in Wp activity in B cell lines, but did not restore promoter activity in n on-B cell lines up to B cell levels. We conclude that CREB/ATF factors are important activators of Wp in a B cell environment but require additional B cell-specific factors in order to mediate their effects.