Identification of a cAMP-response element on the human proopiomelanocortin gene upstream promoter.

Proopiomelanocortin (POMC) is an example of a gene that is stimulated by cAMP without containing the classical cAMP-responsive element on its promoter. To characterize POMC sequences conferring cAMP responsiveness, we used mouse pituitary AtT-20 cells for transient expression of chloramphenicol acetyltransferase reporter gene constructs containing 5'-flanking sequences of the human POMC gene. A novel POMC-cAMP-responsive element (POMC-CRE) was identified, which is located between nucleotides -344 and -319 and which lacks the classical CRE core motif (CGTCA). Using gel retardation assays in combination with antibodies against CREB, we provided evidence that both AtT-20 cell derived and in vitro translated CREB proteins bind to the POMC-CRE and thus may be involved in the stimulation of the gene.