MOLECULAR-CLONING AND CHARACTERIZATION OF THE RAT OVARIAN 20-ALPHA-HYDROXYSTEROID DEHYDROGENASE GENE

The rat 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) is an enz yme responsible for the catabolism of progesterone to the inactive 20 alpha-hydroxyprogesterone. We have previously shown that the expressio n of this enzyme is not regulated by post-translational modification, but at the level of transcription. In this study we have established t hat the 20 alpha-HSD gene contains nine exons and have isolated a 2.5 kb promoter region. The transcription start site was identified and a TATA box was found. 5' deletions of this promoter significantly decrea sed basal promoter activity. Treatment with forskolin led to a dose de pendent inhibition of the 2.5kb-20 alpha-HSD-luciferase construct. Com puter analysis identified one CRE, two Nur77 response elements, two pu tative AP1 sites and one progesterone response element half-site. In s ummary, we have identified and partially characterized the promoter re gion of the rat ovarian 20 alpha-HSD and demonstrated that the regulat ory elements for 20 alpha-HSD are present within a 2.5 kb 5' flanking region of the gene. (C) 1998 Academic Press.