title: Coordinated recruitment of histone methyltransferase G9a and other chromatin-modifying enzymes in SHP-mediated regulation of hepatic bile acid metabolism.
abstract: SHP has been implicated as a pleiotropic regulator of diverse biological functions by its ability to inhibit numerous nuclear receptors. Recently, we reported that SHP inhibits transcription of CYP7A1, a key gene in bile acid biosynthesis, by recruiting histone deacetylases (HDACs) and a Swi/Snf-Brm complex. To further delineate the mechanism of this inhibition, we have examined whether methylation of histones is also involved and whether a functional interplay between chromatin-modifying enzymes occurs. The histone methyltransferase G9a, but not SUV39, was colocalized with SHP in the nucleus and directly interacted with SHP in vitro. G9a, which was coimmunoprecipitated with hepatic SHP, methylated Lys-9 of histone 3 (H3K9) in vitro. Expression of G9a enhanced inhibition of CYP7A1 transcription by SHP, while a catalytically inactive G9a dominant negative (DN) mutant reversed the SHP inhibition. G9a was recruited to and H3K9 was methylated at the CYP7A1 promoter in a SHP-dependent manner in bile acid-treated HepG2 cells. Expression of the G9a-DN mutant inhibited H3K9 methylation, blocked the recruitment of the Brm complex, and partially reversed CYP7A1 inhibition by bile acids. Inhibition of HDAC activity with trichostatin A blocked deacetylation and methylation of H3K9 at the promoter, and, conversely, inhibition of H3K9 methylation by G9a-DN partially blocked deacetylation. Hepatic expression of G9a-DN in mice fed cholic acid disrupted bile acid homeostasis, resulting in increased bile acid pools and partial de-repression of Cyp7a1 and Cyp8b1. Our studies establish a critical role for G9a methyltransferase, histone deacetylases, and the Swi/Snf-Brm complex in the SHP-mediated inhibition of hepatic bile acid synthesis via coordinated chromatin modification at target genes.
authors.affiliation: Department of Molecular and Integrative Physiology, University of Illinois, Urbana, IL 61801, USA.
authors.forename: Sungsoon
authors.initials: S
authors.lastname: Fang
authors.forename: Ji
authors.initials: J
authors.lastname: Miao
authors.forename: Lingjin
authors.initials: L
authors.lastname: Xiang
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Ponugoti
authors.forename: Eckardt
authors.initials: E
authors.lastname: Treuter
authors.forename: Jongsook Kim
authors.initials: JK
authors.lastname: Kemper
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics; D019826:Cholic Acid / Q000378:metabolism* / Q000494:pharmacology; D002843:Chromatin / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006657:Histones / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D008239:Lysine / Q000378:metabolism; D008297:Male; D008745:Methylation / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D011496:Protein Methyltransferases; D021381:Protein Transport / Q000187:drug effects; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D013253:Steroid 12-alpha-Hydroxylase / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D002843:Chromatin; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D018160:Receptors, Cytoplasmic and Nuclear; C099713:nuclear receptor subfamily 0, group B, member 2; C012589:trichostatin A; D002790:Cholesterol 7-alpha-Hydroxylase; D013253:Steroid 12-alpha-Hydroxylase; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D019826:Cholic Acid; D008239:Lysine