Expression of Egr-1 correlates with the transformed phenotype and the type of viral latency in EBV genome positive lymphoid cell lines

In this paper we have investigated the role of Egr-1 in B cell growth regulation by examining the gene expression in a panel of B cell lines, including both EBV genome negative and EBV carrying cell lines. Egr-1 expression correlates with the cellular phenotype and the specific pattern of viral latency established within the individual cell lines. Thus, constitutive activation of Egr-1 gene is invariably associated with unrestricted expression of viral latent genes in all group III EBV genome carrying cell lines. In contrast, Egr-1 expression is abrogated in group I Burkitt tumor cells, irrespective of the EBV genome carrying status. Activated viral gene expression associated with phenotypic conversion of group I cell lines in to group II or III restores the Egr-1 gene expression. Several forms of EGR-1 protein are found within the different groups of cell lines, and the binding activity to DNA consensus sequences was investigated. Finally, time course analysis of Egr-1 expression during the early steps of EBV infection in vitro demonstrated that Egr-1 is upregulated within minutes from the initial interaction with the B lymphocyte.