title: Histone H1 phosphorylation by Cdk2 selectively modulates mouse mammary tumor virus transcription through chromatin remodeling.
abstract: Transcriptional activation of the mouse mammary tumor virus (MMTV) promoter by ligand-bound glucocorticoid receptor (GR) is transient. Previously, we demonstrated that prolonged hormone exposure results in displacement of the transcription factor nuclear factor 1 (NF1) and the basal transcription complex from the promoter, the dephosphorylation of histone H1, and the establishment of a repressive chromatin structure. We have explored the mechanistic link between histone H1 dephosphorylation and silencing of the MMTV promoter by describing the putative kinase responsible for H1 phosphorylation. Both in vitro kinase assays and in vivo protein expression studies suggest that in hormone-treated cells the ability of cdk2 to phosphorylate histone H1 is decreased and the cdk2 inhibitory p21 protein level is increased. To address the role of cdk2 and histone H1 dephosphorylation in the silencing of the MMTV promoter, we used potent cdk2 inhibitors, Roscovitine and CVT-313, to generate an MMTV promoter which is associated predominantly with the dephosphorylated form of histone H1. Both Roscovitine and CVT-313 block phosphorylation of histone H1 and, under these conditions, the GR is unable to remodel chromatin, recruit transcription factors to the promoter, or stimulate MMTV mRNA accumulation. These results suggest a model where cdk2-directed histone H1 phosphorylation is a necessary condition to permit GR-mediated chromatin remodeling and activation of the MMTV promoter in vivo.
authors.affiliation: Department of Obstetrics and Gynaecology, The University of Western Ontario, London, Ontario N6A 4L6, Canada.
authors.forename: R N
authors.initials: RN
authors.lastname: Bhattacharjee
authors.forename: G C
authors.initials: GC
authors.lastname: Banks
authors.forename: K W
authors.initials: KW
authors.lastname: Trotter
authors.forename: H L
authors.initials: HL
authors.lastname: Lee
authors.forename: T K
authors.initials: TK
authors.lastname: Archer
mesh_terms: D000818:Animals; D042846:CDC2-CDC28 Kinases; D002843:Chromatin / Q000502:physiology; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000502:physiology*; D006657:Histones / Q000502:physiology*; D008324:Mammary Tumor Virus, Mouse / Q000502:physiology*; D051379:Mice; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D002843:Chromatin; D006657:Histones; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases