CYTOMEGALOVIRUS MODULATES TRANSCRIPTION FACTORS NECESSARY FOR THE ACTIVATION OF THE TUMOR-NECROSIS-FACTOR-ALPHA PROMOTER

Several studies have demonstrated that cytomegalovirus (CMV) infection increases expression of the tumor necrosis factor (TNF) gene. This ef fect is mediated, in part, by an effect of the CMV immediate early 1 ( IE1) gene product on the TNF promoter. To further analyze these intera ctions, we used plasmids with TNF promoter truncations to determine th e site within the promoter where the CMV IE1 gene product mediates its effect. The site was localized to a 40-base pair segment that contain s a cAMP response element (CREB). Deletion of the cAMP response elemen t increased basal promoter activation but had little effect on IE1-ind uced activation. Additional studies demonstrated that the cAMP element is flanked 5' by a PU.1 site and 3' by an NF-kappa B site, both of wh ich increase expression of the TNF promoter. These sequences demonstra ted IE1 responsiveness. We next determined the relevance of these obse rvations for normal human cells by infecting human alveolar macrophage s with CMV. In these studies we evaluated expression of NF-kappa B, PU .1 and CREB by gel shift assay at Immediate early times after infectio n. We found that CMV infection increased the binding activity of NF-ka ppa B and PU.1 and decreased the binding activity of CREB. CMV infecti on also increased expression of the TNF gene in alveolar macrophages. These observations suggest that CMV increases TNF gene expression, in part, by altering the binding activity of transcription factors that r egulate gene expression.