IDENTIFICATION OF A NEGATIVE CIS-ELEMENT WITHIN THE ZII DOMAIN OF THEEPSTEIN-BARR-VIRUS LYTIC SWITCH BZLF1 GENE PROMOTER

The Epstein-Barr virus (EBV) lytic switch gene, BZLF1, is tightly regu lated in latently infected B cells. The BZLF1 gene promoter (Zp) conta ins several cis elements that have been previously shown to respond to inducers of the viral lytic cycle. These include four copies of an el ement referred to as the ZI domains and an element that contains a con sensus CRE/AP-1 motif (ZII domain). In addition, Zp is autoregulated t hrough two sites that bind the BZLF1 gene product Zta. The ZI domains have been shown to bind the ubiquitous cellular transcription factors Spl and Sp3 and/or the myocyte enhancer factor 2D (Liu et al., EMBO J. 16:143-153, 1997; Liu et al., Virology 228:9-16, 1997). Here we prese nt a functional analysis of the ZII domain and show: (i) ATF-1 and ATF 3 appear to be the predominant cellular factors that bind to the CRE/A P-1 motif present in the ZII domain; and (ii) the region immediately u pstream of the CRE/AP-1 motif contains a potent negative cis element, mutation of which results in a > 10-fold increase in Zp activity. The negative cis element (ZIIR) in the ZII domain decreases both basal and induced Zp activity and thus is likely to play an important role in r egulating reactivation of EBV. In addition, analysis of heterologous p romoter constructs indicates that the function of ZIIR is context sens itive. Attempts to demonstrate a cellular factor binding to ZIIR have been unsuccessful, leaving unresolved the mechanism by which repressio n is mediated.