Activator protein-1 is necessary for angiotensin-II stimulation of human adrenocorticotropin receptor gene transcription

Previous studies have demonstrated that angiotensin-II (A-II) increases the human adrenocorticotropin receptor (hMC2R) gene expression in adrenal cell s. In the present study, we have characterized two activator protein-1 (AP- 1)-binding sites involved in the A-II stimulation of hMC2R gene transcripti on. Vectors containing different fragments of the hMC2R gene promoter inser ted upstream of the luciferase gene, have been constructed. After transfect ion of H295R cells with these constructs and treatment of the cells by A-II during 48 h, maximal stimulation of the luciferase activity was obtained u sing the construct p(-263/+22)luc. Using progressively deleted constructs, three regions responsible for the A-II-stimulated transcription of hMC2R ha ve been delineated. Inside these regions, two sequences displayed some homo logy with an AP-1 binding element (AP-108 and AP-203). Mutation of either A P-108 or AP-203 site induced a decrease of A-II-stimulated luciferase activ ity by 40% and 25%, respectively. Gel-shift analysis showed protein binding to these sites which was increased by an A-II treatment (maximum obtained after 3 h). Moreover, A-II could rapidly increase mRNA levels of several fa ctors belonging to the Fos and Jun families which may be components of the AP-1 complex.