ROLE OF CYCLIC-AMP RESPONSE ELEMENT-BINDING PROTEIN IN CYCLIC-AMP INHIBITION OF NF-KAPPA-B-MEDIATED TRANSCRIPTION

The NF-kappa B family of transcription factors regulates the inducible expression of a variety of genes, Recently, we showed that elevation of intracellular cyclic AMP inhibits NF-kappa B-mediated transcription in human monocytes and endothelial cells without preventing nuclear t ranslocation of NF-kappa B complexes. The present study examined the m olecular mechanism of this inhibition, We hypothesized that activation of the protein kinase A signaling pathway may inhibit NF-kappa B-medi ated transcription by phosphorylating proteins, such as cAMP response element-binding protein (CREB), which compete for limiting amounts of the coactivator CBP, Here, we show that the amino-terminal region (ami no acids 1-450) of CBP specifically interacts with the carboxyl-termin al region (amino acids 286-551) of NF-kappa B p65 (RelA) both in vitro and in vivo. Functional studies using human endothelial cells demonst rated that overexpression of CBP rescued cAMP inhibition of NF-kappa B -mediated transcription and transcription mediated by a chimeric prote in, GAL4-p65(286-551), which contained the GAL4 DNA binding domain fus ed tea the carboxyl-terminal region of p65 (amino acids 286-551), In c ontrast, overexpression of CREB inhibited GAL4-p65(286-551)-mediated t ranscription, These results suggest that activation of the protein kin ase A pathway inhibits NF-kappa B transcription by phosphorylating CRE B, which competes with p65 for limiting amounts of CBP.