Cyril Breuker1, Chris Planque2, Fatemeh Rajabi2, Jean-Charles Nault3, Gabrielle Couchy3, Jessica Zucman-Rossi3, Alexandre Evrard4, Jovana Kantar5, Eric Chevet6, Paulette Bioulac-Sage7, Jeanne Ramos7, Eric Assenat8, Dominique Joubert2, Julie Pannequin2, Frédéric Hollande9, Jean Marc Pascussi10. 1. 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. 2. 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. 3. Institut National de la Santé et de la Recherche Médicale, U674, Paris, France; Université Paris Descartes, Paris, France. 4. 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. 5. Laboratoire de Biochimie, Centre Hospitalier Universitaire, Nîmes, France. 6. Institut National de la Santé et de la Recherche Médicale, U1053, Bordeaux, France. 7. Service d'anatomie pathologique, Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France. 8. Service d'anatomie pathologique, Centre Hospitalier Universitaire Gui de Chauliac, Montpellier, France; Centre Val d'Aurelle, Montpellier, France. 9. 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. 10. 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.
Abstract
BACKGROUND & AIMS: 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.
BACKGROUND & AIMS: 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 humanPXR 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: Tomas Smutny; Lucie Hyrsova; Albert Braeuning; Magnus Ingelman-Sundberg; Petr Pavek Journal: Arch Toxicol Date: 2020-11-09 Impact factor: 5.153
Authors: Matthew C Cave; Heather B Clair; Josiah E Hardesty; K Cameron Falkner; Wenke Feng; Barbara J Clark; Jennifer Sidey; Hongxue Shi; Bashar A Aqel; Craig J McClain; Russell A Prough Journal: Biochim Biophys Acta Date: 2016-03-04
Authors: Ryan A Hlady; Xia Zhao; Xiaoyu Pan; Ju Dong Yang; Fowsiyo Ahmed; Samuel O Antwi; Nasra H Giama; Tushar Patel; Lewis R Roberts; Chen Liu; Keith D Robertson Journal: Theranostics Date: 2019-09-25 Impact factor: 11.556