Am. J. Respir. Cell Mol. Biol., Vol 16, No. 1, Jan 1997, 31-37.
Cytomegalovirus modulates transcription factors necessary for the activation of the tumor necrosis factor-alpha promoter
LJ Geist, HA Hopkins, LY Dai, B He, MM Monick and GW Hunninghake
Department of Medicine, Department of Veterans Affairs, Iowa City, Iowa, USA.
Several studies have demonstrated that cytomegalovirus (CMV) infection
increases expression of the tumor necrosis factor (TNF) gene. This effect
is mediated, in part, by an effect of the CMV immediate early 1 (IE1) gene
product on the TNF promoter. To further analyze these interactions, we used
plasmids with TNF promoter truncations to determine the site within the
promoter where the CMV IE1 gene product mediates its effect. The site was
localized to a 40-base pair segment that contains a cAMP response element
(CREB). Deletion of the cAMP response element increased basal promoter
activation but had little effect on IE1-induced 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 which increase expression of the TNF
promoter. These sequences demonstrated IE1 responsiveness. We next
determined the relevance of these observations for normal human cells by
infecting human alveolar macrophages 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 infection. We found that CMV infection
increased the binding activity of NF-kappa B and PU.1 and decreased the
binding activity of CREB. CMV infection 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 regulate gene expression.
