title: Characterization of a novel PXR isoform with potential dominant-negative properties.
abstract: OBJECTIVE
  The nuclear Pregnane X Receptor (PXR, NR1I2) plays a pivotal role in xenobiotic metabolism. Here, we sought to characterize a new PXR isoform (hereafter called small PXR or sPXR) stemming from alternative transcription starting sites downstream of a CpG Island located near exon 3 of the human PXR gene.
  
  
  METHODS
  Quantitative RT-PCR, western blot, methylation-specific PCR, luciferase reporter assays, electro-mobility shift assays, and stable sPXR overexpression were used to examine sPXR expression and function in hepatocellular cell lines, healthy human liver (n=99), hepatocellular adenomas (HCA, n=91) and hepatocellular carcinoma samples (HCC, n=213).
  
  
  RESULTS
  Liver sPXR mRNA expression varied importantly among individuals and encodes a 37kDa nuclear protein consisting of the ligand-binding domain of PXR that behaves as a dominant-negative of PXR transactivation properties. In vitro methylation of the sPXR upstream promoter abolished its activity, while the demethylation agent 5-aza-2-deoxycytidine increased sPXR mRNA expression in several cell lines. Finally, we observed that sPXR mRNA expression displayed significant differences related to HCA or HCC biology.
  
  
  CONCLUSIONS
  This novel PXR isoform, displaying a dominant-negative activity and regulated by DNA methylation, is associated with outcomes of patients with HCC treated by resection, suggesting that it represents a key modulator of PXR.
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France; Service de Pharmacie, Centre Hospitalier Universitaire Lapeyronie, Montpellier, France.
authors.forename: Cyril
authors.initials: C
authors.lastname: Breuker
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France.
authors.forename: Chris
authors.initials: C
authors.lastname: Planque
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Rajabi
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, U674, Paris, France; Université Paris Descartes, Paris, France.
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Nault
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, U674, Paris, France; Université Paris Descartes, Paris, France.
authors.forename: Gabrielle
authors.initials: G
authors.lastname: Couchy
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, U674, Paris, France; Université Paris Descartes, Paris, France.
authors.forename: Jessica
authors.initials: J
authors.lastname: Zucman-Rossi
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France; Laboratoire de Biochimie, Centre Hospitalier Universitaire, Nîmes, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Evrard
authors.affiliation: Laboratoire de Biochimie, Centre Hospitalier Universitaire, Nîmes, France.
authors.forename: Jovana
authors.initials: J
authors.lastname: Kantar
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, U1053, Bordeaux, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Chevet
authors.affiliation: Service d'anatomie pathologique, Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France.
authors.forename: Paulette
authors.initials: P
authors.lastname: Bioulac-Sage
authors.affiliation: Service d'anatomie pathologique, Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France.
authors.forename: Jeanne
authors.initials: J
authors.lastname: Ramos
authors.affiliation: Service d'anatomie pathologique, Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France; Centre Val d'Aurelle, Montpellier, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Assenat
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Joubert
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Pannequin
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France; Department of Pathology, University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Hollande
authors.affiliation: Centre National de la Recherche Scientifique, UMR5203, Institut de Génomique Fonctionnelle, Montpellier, France; Institut National de la Santé et de la Recherche Médicale, U661, Montpellier, France; Université Montpellier 1 et 2, UMR5203, Montpellier, France. Electronic address: jean-marc.pascussi@inserm.fr.
authors.forename: Jean Marc
authors.initials: JM
authors.lastname: Pascussi
mesh_terms: D018248:Adenoma, Liver Cell / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D019175:DNA Methylation; D006498:Hepatectomy; D006801:Humans; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D000077297:Pregnane X Receptor; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D016896:Treatment Outcome
chemical_list: C000625852:NR1I2 protein, human; D000077297:Pregnane X Receptor; D020033:Protein Isoforms; D012333:RNA, Messenger; D011987:Receptors, Steroid
keywords: Drug metabolism; Epigenetic regulation; Hepatocyte; Nuclear receptor