RT Journal Article SR Electronic T1 Inhibition of Cyclic AMP Response Element-Binding Protein/Cyclic AMP Response Element-Mediated Transcription by the Immunosuppressive Drugs Cyclosporin A and FK506 Depends on the Promoter Context JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1094 OP 1100 DO 10.1124/mol.55.6.1094 VO 55 IS 6 A1 Siemann, Gero A1 Blume, Roland A1 Grapentin, Daniela A1 Oetjen, Elke A1 Schwaninger, Markus A1 Knepel, Willhart YR 1999 UL http://molpharm.aspetjournals.org/content/55/6/1094.abstract AB The immunosuppressants cyclosporin A and FK506 (tacrolimus) can block the phosphatase calcineurin, thereby inhibiting gene transcription directed by the cyclic AMP (cAMP)- and calcium-responsive transcription factor, cAMP response element (CRE)-binding protein, and its binding site, CRE, in various cell lines. This action is a novel molecular mechanism of cyclosporin A and FK506 action. Because inhibition of CREB/CRE-directed transcription by cyclosporin A and FK506 has previously been observed by using synthetic minienhancers, reporter fusion genes were constructed to examine the effect of cyclosporin A and FK506 on the transcriptional activity of CRE-containing natural promoters. In transient transfection experiments, cyclosporin A and FK506 inhibited the transcriptional activation by cAMP and the membrane depolarization of three CRE-containing promoters. However, cyclosporin A and FK506 failed to inhibit the activation by cAMP of another promoter, the rat insulin I gene promoter. The lack of cyclosporin A/FK506 sensitivity is not intrinsic to the insulin CRE because cyclosporin A and FK506 inhibited the activation by cAMP of the insulin CRE when isolated and used as a synthetic minienhancer. Rather, cyclosporin A/FK506 resistance may be conferred by specific promoter interactions because a mutational analysis of the insulin promoter revealed that inside this promoter, CRE activity depends on an adjacent control element. These data show that cyclosporin A and FK506 can inhibit CRE activity when the CRE resides in its natural promoter. However, the cyclosporin A/FK506 sensitivity depends on the specific promoter context. The results suggest that cyclosporin A and FK506 may alter target tissue function through the regulation of a subset of CRE-containing genes.