Molecular Cloning and Characterization of the Rat Ovarian 20α-Hydroxysteroid Dehydrogenase Gene

The rat 20α-hydroxysteroid dehydrogenase (20α-HSD) is an enzyme responsible for the catabolism of progesterone to the inactive 20α-hydroxyprogesterone. We have previously shown that the expression of this enzyme is not regulated by post-translational modification, but at the level of transcription. In this study we have established that the 20α-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 decreased basal promoter activity. Treatment with forskolin led to a dose dependent inhibition of the 2.5kb-20α-HSD-luciferase construct. Computer analysis identified one CRE, two Nur77 response elements, two putative AP1 sites and one progesterone response element half-site. In summary, we have identified and partially characterized the promoter region of the rat ovarian 20α-HSD and demonstrated that the regulatory elements for 20α-HSD are present within a 2.5 kb 5′ flanking region of the gene.