title: AP-2 gamma and the homeodomain protein distal-less 3 are required for placental-specific expression of the murine 3 beta-hydroxysteroid dehydrogenase VI gene, Hsd3b6.
abstract: The enzyme 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) is essential for the biosynthesis of all active steroid hormones. It exists as multiple isoforms in humans and rodents, each the product of a distinct gene. Human 3 beta-HSD I in placenta is essential for placental progesterone biosynthesis and thus is essential for the maintenance of pregnancy. The murine ortholog, 3 beta-HSD VI, is the only isoform expressed in giant trophoblast cells during the first half of mouse pregnancy. This study was designed to identify the cis-acting element(s) and the associated transcription factors required for trophoblast-specific expression of 3 beta-HSD VI. Transfection studies in placental and nonplacental cells identified a novel 66-bp trophoblast-specific enhancer element located between -2896 and -2831 of the 3 beta-HSD VI promoter. DNase protection analysis of the enhancer element identified three trophoblast-specific binding sites, FPI, FPII, and FPIII. Electrophoretic mobility shift assays with oligonucleotides representing the protected sequences, FPI and FPIII, and nuclear extracts isolated from human JEG-3 cells and from mouse trophoblast cells, demonstrated the same binding pattern that was distinct from the binding pattern with mouse Leydig cell nuclear proteins. Further electrophoretic mobility shift assays identified AP-2 gamma and the homeodomain protein, Dlx 3, as the transcription factors that specifically bind to FPI and FPIII, respectively. Site-specific mutations in each of the binding sites eliminated enhancer activity indicating that AP-2 gamma and Dlx 3, together with an additional transcription factor(s) that are conserved between humans and mice, are required for trophoblast-specific expression of 3 beta-HSD VI.
authors.affiliation: Division of Reproductive Biology, Department of Gynecology and Obstetrics, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Lihong
authors.initials: L
authors.lastname: Peng
authors.forename: Anita H
authors.initials: AH
authors.lastname: Payne
mesh_terms: D015067:17-Hydroxysteroid Dehydrogenases / Q000235:genetics*; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology*; D003850:Deoxyribonuclease I / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005091:Exons; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000502:physiology*; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010920:Placenta / Q000201:enzymology / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000737:chemistry* / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; C088334:Distal-less homeobox proteins; D018398:Homeodomain Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C493679:TFAP2C protein, human; C583890:Tfap2c protein, mouse; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D015067:17-Hydroxysteroid Dehydrogenases; C044256:3 (or 17)-beta-hydroxysteroid dehydrogenase; D008156:Luciferases; D003850:Deoxyribonuclease I