title: The farnesoid X receptor induces fetuin-B gene expression in human hepatocytes.
abstract: FXR (farnesoid X receptor), a nuclear receptor activated by BAs (bile acids), is a key factor in the regulation of BA, lipid and carbohydrate metabolism. The recent development of synthetic FXR agonists and knockout mouse models has accelerated the discovery of FXR target genes. In the present study, we identify human fetuin-B as a novel FXR target gene. Treatment with FXR agonists increased fetuin-B expression in human primary hepatocytes and in the human hepatoma HepG2 cell line. In contrast, fetuin-B expression was not responsive to FXR agonist treatment in murine primary hepatocytes. Fetuin-B induction by FXR agonist was abolished upon FXR knockdown by siRNA (small interfering RNA). In addition to the previously described P1 promoter, we show that the human fetuin-B gene is also transcribed from an alternative promoter, termed P2. Transcription via the P2 promoter was induced by FXR agonist treatment, whereas P1 promoter activity was not sensitive to FXR agonist treatment. Two putative FXR-response elements [IR-1 (inverted repeat-1)] were identified in the region -1.6 kb upstream of the predicted P2 transcriptional start site. Both motifs bound FXR-RXR (retinoid X receptor) complexes in vitro and were activated by FXR in transient transfection reporter assays. Mutations in the IR-1 sites abolished FXR-RXR binding and activation. Taken together, these results identify human fetuin-B as a new FXR target gene in human hepatocytes.
authors.affiliation: Tokyo New Research Laboratories I, Pharmaceutical Division, Kowa Company Ltd, 2-17-43 Noguchicho, Higashimurayama, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Murakami
authors.forename: Robert
authors.initials: R
authors.lastname: Walczak
authors.forename: Sandrine
authors.initials: S
authors.lastname: Caron
authors.forename: Christian
authors.initials: C
authors.lastname: Duhem
authors.forename: Vincent
authors.initials: V
authors.lastname: Vidal
authors.forename: Raphaël
authors.initials: R
authors.lastname: Darteil
authors.forename: Bart
authors.initials: B
authors.lastname: Staels
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000819:agonists / Q000502:physiology*; D060752:Fetuin-B; D020869:Gene Expression Profiling; D022781:Hepatocytes / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000502:physiology*; D014157:Transcription Factors / Q000819:agonists / Q000502:physiology*; D015854:Up-Regulation / Q000502:physiology*; D000509:alpha-Fetoproteins / Q000096:biosynthesis* / Q000235:genetics*; D000099150:Receptor, Farnesoid X-Activated
chemical_list: D004268:DNA-Binding Proteins; D060752:Fetuin-B; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D000509:alpha-Fetoproteins; D000099150:Receptor, Farnesoid X-Activated; C504687:FETUB protein, human