title: Control of gene expression by the retinoic acid-related orphan receptor alpha in HepG2 human hepatoma cells.
abstract: Retinoic acid-related Orphan Receptor alpha (RORα; NR1F1) is a widely distributed nuclear receptor involved in several (patho)physiological functions including lipid metabolism, inflammation, angiogenesis, and circadian rhythm. To better understand the role of this nuclear receptor in liver, we aimed at displaying genes controlled by RORα in liver cells by generating HepG2 human hepatoma cells stably over-expressing RORα. Genes whose expression was altered in these cells versus control cells were displayed using micro-arrays followed by qRT-PCR analysis. Expression of these genes was also altered in cells in which RORα was transiently over-expressed after adenoviral infection. A number of the genes found were involved in known pathways controlled by RORα, for instance LPA, NR1D2 and ADIPOQ in lipid metabolism, ADIPOQ and PLG in inflammation, PLG in fibrinolysis and NR1D2 and NR1D1 in circadian rhythm. This study also revealed that genes such as G6PC, involved in glucose homeostasis, and AGRP, involved in the control of body weight, are also controlled by RORα. Lastly, SPARC, involved in cell growth and adhesion, and associated with liver carcinogenesis, was up-regulated by RORα. SPARC was found to be a new putative RORα target gene since it possesses, in its promoter, a functional RORE as evidenced by EMSAs and transfection experiments. Most of the other genes that we found regulated by RORα also contained putative ROREs in their regulatory regions. Chromatin immunoprecipitation (ChIP) confirmed that the ROREs present in the SPARC, PLG, G6PC, NR1D2 and AGRP genes were occupied by RORα in HepG2 cells. Therefore these genes must now be considered as direct RORα targets. Our results open new routes on the roles of RORα in glucose metabolism and carcinogenesis within cells of hepatic origin.
authors.affiliation: Laboratoire de Pharmacologie, Toxicologie et Signalisation Cellulaire, INSERM UMR-S-747, Centre Universitaire des Saints Pères, Université Paris Descartes, Paris, France. caroline.chauvet@parisdescartes.fr
authors.forename: Caroline
authors.initials: C
authors.lastname: Chauvet
authors.forename: Amandine
authors.initials: A
authors.lastname: Vanhoutteghem
authors.forename: Christian
authors.initials: C
authors.lastname: Duhem
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Saint-Auret
authors.forename: Brigitte
authors.initials: B
authors.lastname: Bois-Joyeux
authors.forename: Philippe
authors.initials: P
authors.lastname: Djian
authors.forename: Bart
authors.initials: B
authors.lastname: Staels
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Danan
mesh_terms: D000256:Adenoviridae / Q000378:metabolism; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000235:genetics*; D047369:Chromatin Immunoprecipitation; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics*; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1 / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D015676:Osteonectin / Q000235:genetics; D011485:Protein Binding; D020218:Response Elements / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D015854:Up-Regulation / Q000235:genetics
chemical_list: D009363:Neoplasm Proteins; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D015676:Osteonectin; C539738:RORA protein, human