title: The Ah receptor recruits IKKα to its target binding motifs to phosphorylate serine-10 in histone H3 required for transcriptional activation.
abstract: Aryl hydrocarbon receptor (AHR) activation by xenobiotic ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is key to their toxicity. Following activation and nuclear translocation, AHR heterodimerizes with the AHR nuclear translocator (ARNT) and binds to AHR response elements (AhREs) in the enhancer of target genes, of which Cyp1a1 is the prototype. Previously, we showed that concomitant with AHR binding, histone H3 in the Cyp1a1 enhancer-promoter AhRE cluster became phosphorylated in serine-10 (H3S10), suggesting that the ligand-activated AHR recruited one or more kinases to the enhancer chromatin to phosphorylate this residue. To test this hypothesis, we used mouse hepatoma Hepa-1c1c7 cells and their c35 mutant derivative, lacking a functional AHR, to search for candidate kinases that would phosphorylate H3S10 in an AHR dependent manner. Using chromatin immunoprecipitation with antibodies to a comprehensive set of protein kinases, we identified three kinases, IκB kinase α (IKKα), mitogen and stress activated protein kinase 1 (MSK1), and mitogen and stress activated protein kinase 2 (MSK2), whose binding to the Cyp1a1 enhancer was significantly increased by TCDD in Hepa-1c1c7 cells and absent in control c35 cells. Complexes of AHR, ARNT, and IKKα could be coimmunoprecipitated from nuclei of TCDD treated Hepa-1c1c7 cells and shRNA-mediated IKKα knockdown inhibited both H3S10 phosphorylation in the Cyp1a1 enhancer and the induction of Cyp1a1, Aldh3a1, and Nqo1 in TCDD-treated cells. We conclude that AHR recruits IKKα to the promoter of its target genes and that AHR-mediated H3S10 phosphorylation is a key epigenetic requirement for induction of AHR targets. Given the role of H3S10ph in regulation of chromosome condensation, AHR-IKKα cross-talk may be a mediator of chromatin remodeling by environmental agents.
authors: Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati, College of Medicine, 3223 Eden Avenue, Cincinnati, OH 45267.
authors: Hisaka
authors: H
authors: Kurita
authors: Michael
authors: M
authors: Schnekenburger
authors: Jerald L
authors: JL
authors: Ovesen
authors: Ying
authors: Y
authors: Xia
authors: Alvaro
authors: A
authors: Puga
mesh_terms: D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D019281:Dimerization; D004742:Enhancer Elements, Genetic; D006657:Histones / Q000737:chemistry / Q000378:metabolism*; D051550:I-kappa B Kinase / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D016133:Polymerase Chain Reaction; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism / Q000502:physiology*; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D012694:Serine / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D006657:Histones; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D012694:Serine; D019363:Cytochrome P-450 CYP1A1; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C485459:Rps6ka4 protein, mouse; C116919:mitogen and stress-activated protein kinase 1; D051550:I-kappa B Kinase
keywords: aryl hydrocarbon receptor; chromatin histone modifications; epigenetics; gene regulation; inhibitor of nuclear factor kappa-B kinase subunit alpha; protein kinases