title: Cell cycle phase regulates glucocorticoid receptor function.
abstract: The glucocorticoid receptor (GR) is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. In contrast to many other nuclear receptors, GR is thought to be exclusively cytoplasmic in quiescent cells, and only translocate to the nucleus on ligand binding. We now demonstrate significant nuclear GR in the absence of ligand, which requires nuclear localisation signal 1 (NLS1). Live cell imaging reveals dramatic GR import into the nucleus through interphase and rapid exclusion of the GR from the nucleus at the onset of mitosis, which persists into early G(1). This suggests that the heterogeneity in GR distribution is reflective of cell cycle phase. The impact of cell cycle-driven GR trafficking on a panel of glucocorticoid actions was profiled. In G2/M-enriched cells there was marked prolongation of glucocorticoid-induced ERK activation. This was accompanied by DNA template-specific, ligand-independent GR transactivation. Using chimeric and domain-deleted receptors we demonstrate that this transactivation effect is mediated by the AF1 transactivation domain. AF-1 harbours multiple phosphorylation sites, which are consensus sequences for kinases including CDKs, whose activity changes during the cell cycle. In G2/M there was clear ligand independent induction of GR phosphorylation on residues 203 and 211, both of which are phosphorylated after ligand activation. Ligand-independent transactivation required induction of phospho-S211GR but not S203GR, thereby directly linking cell cycle driven GR modification with altered GR function. Cell cycle phase therefore regulates GR localisation and post-translational modification which selectively impacts GR activity. This suggests that cell cycle phase is an important determinant in the cellular response to Gc, and that mitotic index contributes to tissue Gc sensitivity.
authors.affiliation: Developmental Biomedicine Research Group, University of Manchester, Manchester, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Matthews
authors.forename: James
authors.initials: J
authors.lastname: Johnson
authors.forename: Andrew
authors.initials: A
authors.lastname: Berry
authors.forename: Peter
authors.initials: P
authors.lastname: Trebble
authors.forename: Ann
authors.initials: A
authors.lastname: Cookson
authors.forename: Dave
authors.initials: D
authors.lastname: Spiller
authors.forename: Caroline
authors.initials: C
authors.lastname: Rivers
authors.forename: Michael
authors.initials: M
authors.lastname: Norman
authors.forename: Mike
authors.initials: M
authors.lastname: White
authors.forename: David
authors.initials: D
authors.lastname: Ray
mesh_terms: D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008938:Mitosis / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D019913:Nuclear Localization Signals; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D011965:Receptors, Glucocorticoid / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D019913:Nuclear Localization Signals; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone