title: Transcriptional regulation of mouse PXR gene: an interplay of transregulatory factors.
abstract: Pregnane X Receptor (PXR) is an important ligand-activated nuclear receptor functioning as a 'master regulator' of expression of phase I, phase II drug metabolizing enzymes, and members of the drug transporters. PXR is primarily expressed in hepatic tissues and to lesser extent in other non-hepatic tissues both in human and in mice. Although its expression profile is well studied but little is known about the regulatory mechanisms that govern PXR gene expression in these cells. In the present study, we have cloned and characterized over 5 kb (-4963 to +54) region lying upstream of mouse PXR transcription start site. Promoter-reporter assays revealed that the proximal promoter region of up to 1 kb is sufficient to support the expression of PXR in the mouse liver cell lines. It was evident that the 500 bp proximal promoter region contains active binding sites for Ets, Tcf, Ikarose and nuclear factor families of transcription factors. Electrophoretic mobility shift assays demonstrated that the minimal region of 134 bp PXR promoter was able to bind Ets-1 and β-catenin proteins. This result was further confirmed by chromatin immunoprecipitation analysis. In summary, the present study identified a promoter region of mouse PXR gene and the transregulatory factors responsible for PXR promoter activity. The results presented herein are expected to provide important cues to gain further insight into the regulatory mechanisms of PXR function.
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Kumari
authors.forename: Gauranga
authors.initials: G
authors.lastname: Mukhopadhyay
authors.forename: Rakesh K
authors.initials: RK
authors.lastname: Tyagi
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D047369:Chromatin Immunoprecipitation; D003001:Cloning, Molecular; D019295:Computational Biology; D004247:DNA / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D000077297:Pregnane X Receptor; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D025941:Protein Interaction Mapping; D050784:Proto-Oncogene Protein c-ets-1 / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D017384:Sequence Deletion; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D051176:beta Catenin / Q000378:metabolism
chemical_list: C497574:Lef1 protein, mouse; D051821:Lymphoid Enhancer-Binding Factor 1; D000077297:Pregnane X Receptor; D050784:Proto-Oncogene Protein c-ets-1; D011987:Receptors, Steroid; D014157:Transcription Factors; D051176:beta Catenin; D004247:DNA; D008156:Luciferases