cAMP and tumor necrosis factor competitively regulate transcriptional activation through and nuclear factor binding...

The cAMP-responsive element/activating transcription factor (CRE/ATF) element (also known as NF-ELAM1) of the endothelial leukocyte adhesion molecule-1 (ELAM-1) promoter is necessary for full cytokine responsiveness. It differs from a consensus cAMP-responsive element (CRE) by 1 nucleotide (G-->A conversion) and does not mediate transcriptional activation in response to cAMP. We reported previously that cAMP actually decreases ELAM-1 synthesis induced by tumor necrosis factor (TNF). We now show that cAMP decreases the ELAM-1 promoter response to TNF in transient transfection assays in bovine aortic endothelial cells and that cAMP-mediated inhibition maps to the CRE/ATF element. Electrophoretic mobility shift assays using the ELAM-1 CRE/ATF DNA sequence reveal three complexes. Antibody supershift assays suggest the slowest migrating form (complex 1) contains ATF2, the middle form (complex 2) contains ATF2 and c-Jun, and the fastest migrating form (complex 3) contains a CRE-binding protein. TNF increases c-Jun-containing complex 2 while diminishing complex 1, whereas cAMP decreases complex 2 and increases complex 1. Complex 3 is unchanged by either treatment, and the CRE-binding protein is not phosphorylated. Our data suggest that a change in the composition of the proteins binding to the CRE/ATF promoter element contributes to the competing effects of TNF and cAMP on ELAM-1 gene expression.