title: Transcriptional synergism between vitamin D-responsive elements in the rat 25-hydroxyvitamin D3 24-hydroxylase (CYP24) promoter.
abstract: Transcription of the CYP24 gene is induced by 1,25-(OH)2D3 through a vitamin D receptor-dependent process. The functional activities of three possible vitamin D response elements (VDREs), located on the antisense strand of the rat CYP24 promoter, were investigated by transient expression of native and mutant promoter constructs in COS-1, JTC-12, and ROS 17/2.8 cells. A putative VDRE with a half-site spacing of 6 base pairs at -249/-232 (VDRE-3) did not contribute to 1,25-(OH)2D3 induced expression in the native promoter, although activity has been reported when the element was fused to the heterologous thymidine kinase promoter. Two VDREs with half-site spacings of 3 base pairs at -150/-136 and -258/-244 (VDRE-1 and VDRE-2, respectively), showed transcriptional synergism in COS-1 cells when treated with 1,25-(OH)2D3 (10(-7) to 10(-11) M). The contribution of both VDREs was hormone-concentration dependent from 10(-10) to 10(-12) M, with VDRE-1 demonstrating greatest sensitivity to 1,25-(OH)2D3. Transactivation by VDRE-1 was always greater than VDRE-2, but the converse was observed for the binding of vitamin D receptor-retinoid X receptor complex by each VDRE in gel mobility shift assays. The synergy observed between VDRE-1 and VDRE-2 may have important implications in cellular responses to different circulating levels of 1,25-(OH)2D3.
authors.affiliation: Department of Biochemistry, University of Adelaide, Adelaide, South Australia 5005, Australia. omdahl@medusa.unm.edu
authors.forename: D M
authors.initials: DM
authors.lastname: Kerry
authors.forename: P P
authors.initials: PP
authors.lastname: Dwivedi
authors.forename: C N
authors.initials: CN
authors.lastname: Hahn
authors.forename: H A
authors.initials: HA
authors.lastname: Morris
authors.forename: J L
authors.initials: JL
authors.lastname: Omdahl
authors.forename: B K
authors.initials: BK
authors.lastname: May
mesh_terms: D000818:Animals; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D013250:Steroid Hydroxylases / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014807:Vitamin D / Q000378:metabolism*; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D009687:Nuclear Proteins; D014807:Vitamin D; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase