title: Epigenetic mechanisms in the dopamine D2 receptor-dependent inhibition of the prolactin gene.
abstract: Transcription of the prolactin gene is dynamically controlled by positive and negative hormone signals that target the regulatory promoter region. Based on the inducibility of prolactin gene expression by inhibitors of histone deacetylases (HDACs), we examined the role of histone acetylation at the genomic prolactin promoter as a late step in transcriptional regulation. Chromatin immunoprecipitation analysis of GH4 cells revealed elevated levels of acetylated histones in the promoter and enhancer regions of the gene, compared with downstream intron sequences. 17beta-Estradiol stimulated histone H4 acetylation in the promoter region by 2- to 3-fold within 30 min. Dopamine inhibited histone H4 acetylation by 2-fold in 30 min, an effect mimicked by the MAPK kinase (MEK1) inhibitor U0126. In contrast, the synthetic glucocorticoid dexamethasone, which inhibits prolactin transcription, failed to alter histone acetylation over the same time frame. Association of transcription activator Pit-1 with the prolactin promoter was unchanged by hormone treatment. However, in response to dopamine, histone deacetylase HDAC2 and corepressor mSin3A were rapidly recruited to the prolactin promoter, and association was sustained above basal levels over a 1-h period. Consistent with this corepressor function, depletion of endogenous mSin3A by small interfering RNA was sufficient to enhance prolactin gene expression by 70%, comparable to the induction by the HDAC inhibitor, trichostatin A. These studies demonstrate that dopamine D2 receptor activation and inhibition of MAPK (ERK1/2) signaling lead to rapid deacetylation of histones at the genomic prolactin promoter. Recruitment of specific HDAC/ corepressor complexes may be an important mechanism for repression of target gene transcription by Gi/o-coupled receptors.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, 100 College Street, Toronto, Ontario, Canada M5G 1L5.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Liu
authors.forename: Ross E
authors.initials: RE
authors.lastname: Baker
authors.forename: Winsion
authors.initials: W
authors.lastname: Chow
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Sun
authors.forename: Harry P
authors.initials: HP
authors.lastname: Elsholtz
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000818:Animals; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology; D015536:Down-Regulation / Q000235:genetics; D004742:Enhancer Elements, Genetic / Q000235:genetics; D044127:Epigenesis, Genetic; D004958:Estradiol / Q000494:pharmacology; D056464:Histone Deacetylase 2; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism*; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors; D010902:Pituitary Gland / Q000378:metabolism*; D011388:Prolactin / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000819:agonists* / Q000502:physiology; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D056264:Sin3 Histone Deacetylase and Corepressor Complex; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D004298:Dopamine; D004958:Estradiol; D056464:Histone Deacetylase 2; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases; D006657:Histones; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D011388:Prolactin; D017448:Receptors, Dopamine D2; D012097:Repressor Proteins; D056264:Sin3 Histone Deacetylase and Corepressor Complex; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; C494187:POU1F1 protein, human; C494185:Pou1f1 protein, mouse; C494186:Pou1f1 protein, rat; C099683:SIN3A transcription factor; C533424:Hdac2 protein, mouse; C533426:Hdac2 protein, rat