title: Hormone-mediated dephosphorylation of specific histone H1 isoforms.
abstract: We have previously shown a connection between histone H1 phosphorylation and the transcriptional competence of the hormone inducible mouse mammary tumor virus (MMTV) promoter. Prolonged exposure of mouse cells to dexamethasone concurrently dephosphorylated histone H1 and rendered the MMTV promoter refractory to hormonal stimulation and, therefore, transcriptionally unresponsive. Using electrospray mass spectrometry, we demonstrate here that prolonged dexamethasone treatment differentially effects a subset of the six somatic H1 isoforms in mouse cells. H1 isoforms H1.0, H1.1, and H1.2 are non-responsive to hormone whereas prolonged dexamethasone treatment effectively dephosphorylated the H1.3, H1.4, and H1.5 isoforms. The protein kinase inhibitor staurosporine, shown to dephosphorylate histone H1 and down-regulate MMTV in cultured cells, appears only to completely dephosphorylate the H1.3 isoform. These results suggest that dephosphorylation of specific histone H1 isoforms may contribute to the previously observed decrease in transcriptional competence of the MMTV promoter through the modulation of chromatin structure. In a broader sense, this work advances the hypothesis that post-translational modifications of individual histone H1 isoforms directly influence the transcriptional activation/repression of specific genes.
authors.affiliation: Laboratories of Reproductive and Developmental Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
authors.forename: G C
authors.initials: GC
authors.lastname: Banks
authors.forename: L J
authors.initials: LJ
authors.lastname: Deterding
authors.forename: K B
authors.initials: KB
authors.lastname: Tomer
authors.forename: T K
authors.initials: TK
authors.lastname: Archer
mesh_terms: D000818:Animals; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003907:Dexamethasone / Q000494:pharmacology; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006657:Histones / Q000737:chemistry* / Q000378:metabolism*; D006728:Hormones / Q000494:pharmacology*; D051379:Mice; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D021241:Spectrometry, Mass, Electrospray Ionization; D019311:Staurosporine / Q000494:pharmacology; D014158:Transcription, Genetic
chemical_list: D018931:Antineoplastic Agents, Hormonal; D004791:Enzyme Inhibitors; D006657:Histones; D006728:Hormones; D020033:Protein Isoforms; D003907:Dexamethasone; D019311:Staurosporine