title: Transcriptional analysis of the orphan nuclear receptor constitutive androstane receptor (NR1I3) gene promoter: identification of a distal glucocorticoid response element.
abstract: The constitutive androstane receptor (CAR, NR1I3) transcriptionally activates cytochrome P450 2B6, 2C9, and 3A4 when activated by xenobiotics, such as phenobarbital. Information on the human CAR promoter was obtained by searching the NCBI human genome database. A contig (NT026945) corresponding to a fragment of chromosome 1q21 was found to contain the complete CAR gene. These data were confirmed using chromosomal in situ hybridization. Both primer extension and 5'-rapid amplification of the cDNA end PCR analysis were carried out to determine the transcriptional start site of human CAR, which was found to be 32 nucleotides downstream of a potential TATA box (CATAAAA). In addition, we found that the 5'-untranslated region of CAR mRNA is 110 nucleotides shorter than previously reported. Using genomic PCR, we amplified and cloned approximately 4.9 kb (-4711/+144) of the CAR gene promoter. The activity of this promoter was measured by transient transfection. Deletion analysis suggested the presence of a glucocorticoid responsive element in its distal region (-4477/-4410). From cotransfection experiments, mutagenesis, and gel shift assays, we identified a glucocorticoid response element at -4447/-4432 that was recognized and transactivated by the human glucocorticoid receptor. Finally, using the chromatin immunoprecipitation assay, we demonstrated that the glucocorticoid receptor binds to the distal region of CAR promoter in cultured hepatocytes only in the presence of dexamethasone. Identification of this functional element provides a rational mechanistic basis for CAR induction by glucocorticoids. CAR appears to be a primary glucocorticoid receptor-response gene.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Fédératif de Recherche No 24, 34293 Montpellier, France. pascussi@montp.inserm.fr
authors.forename: Jean Marc
authors.initials: JM
authors.lastname: Pascussi
authors.forename: Maryvonne
authors.initials: M
authors.lastname: Busson-Le Coniat
authors.forename: Patrick
authors.initials: P
authors.lastname: Maurel
authors.forename: Marie-José
authors.initials: MJ
authors.lastname: Vilarem
mesh_terms: D002478:Cells, Cultured; D003001:Cloning, Molecular; D000090702:Constitutive Androstane Receptor; D005786:Gene Expression Regulation; D022781:Hepatocytes; D006801:Humans; D011401:Promoter Regions, Genetic / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D011965:Receptors, Glucocorticoid / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D020218:Response Elements / Q000235:genetics*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D014158:Transcription, Genetic; D015533:Transcriptional Activation / Q000502:physiology
chemical_list: D000090702:Constitutive Androstane Receptor; C000716327:NR1I3 protein, human; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D011965:Receptors, Glucocorticoid; D014157:Transcription Factors