title: Plasticity of HP1 proteins in mammalian cells.
abstract: We have compared the distribution of endogenous heterochromatin protein 1 (HP1) proteins (alpha, beta and gamma) in different epithelial lines, pluripotent stem cells and embryonic fibroblasts. In parallel, we have interrogated assembly and dynamics of newly expressed HP1-GFP proteins in cells lacking both HP1alpha and HP1beta alleles, blocked at the G1-S boundary, or cultured in the presence of HDAC and HAT inhibitors. The results reveal a range of cell type and differentiation state-specific patterns that do not correlate with 'fast' or 'slow' subunit exchange in heterochromatin. Furthermore, our observations show that targeting of HP1gamma to heterochromatic sites depends on HP1alpha and H1beta and that, on an architectural level, HP1alpha is the most polymorphic variant of the HP1 family. These data provide evidence for HP1 plasticity under shifting microenvironmental conditions and offer a new conceptual framework for understanding chromatin dynamics at the molecular level.
authors.affiliation: The Stem Cell and Chromatin Group, Laboratory of Biology, The University of Ioannina, School of Medicine and The Institute of Biomedical Research (FORTH/BRI), 45 110 Ioannina, Greece.
authors.forename: George K
authors.initials: GK
authors.lastname: Dialynas
authors.forename: Stefan
authors.initials: S
authors.lastname: Terjung
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Brown
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Aucott
authors.forename: Bettina
authors.initials: B
authors.lastname: Baron-Luhr
authors.forename: Prim B
authors.initials: PB
authors.lastname: Singh
authors.forename: Spyros D
authors.initials: SD
authors.lastname: Georgatos
mesh_terms: D000818:Animals; D002460:Cell Line; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D006570:Heterochromatin / Q000378:metabolism; D006801:Humans; D051379:Mice; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C000715593:CBX1 protein, human; C000715594:CBX5 protein, human; D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D000090266:Chromobox Protein Homolog 5