title: Pericentromeric heterochromatin domains are maintained without accumulation of HP1.
abstract: The heterochromatin protein 1 (HP1) family is thought to be an important structural component of heterochromatin. HP1 proteins bind via their chromodomain to nucleosomes methylated at lysine 9 of histone H3 (H3K9me). To investigate the role of HP1 in maintaining heterochromatin structure, we used a dominant negative approach by expressing truncated HP1alpha or HP1beta proteins lacking a functional chromodomain. Expression of these truncated HP1 proteins individually or in combination resulted in a strong reduction of the accumulation of HP1alpha, HP1beta, and HP1gamma in pericentromeric heterochromatin domains in mouse 3T3 fibroblasts. The expression levels of HP1 did not change. The apparent displacement of HP1alpha, HP1beta, and HP1gamma from pericentromeric heterochromatin did not result in visible changes in the structure of pericentromeric heterochromatin domains, as visualized by DAPI staining and immunofluorescent labeling of H3K9me. Our results show that the accumulation of HP1alpha, HP1beta, and HP1gamma at pericentromeric heterochromatin domains is not required to maintain DAPI-stained pericentromeric heterochromatin domains and the methylated state of histone H3 at lysine 9 in such heterochromatin domains.
authors.affiliation: Swammerdam Institute for Life Sciences, BioCentrum Amsterdam, University of Amsterdam, 1098 SM Amsterdam, The Netherlands.
authors.forename: Julio
authors.initials: J
authors.lastname: Mateos-Langerak
authors.forename: Maartje C
authors.initials: MC
authors.lastname: Brink
authors.forename: Martijn S
authors.initials: MS
authors.lastname: Luijsterburg
authors.forename: Ineke
authors.initials: I
authors.lastname: van der Kraan
authors.forename: Roel
authors.initials: R
authors.lastname: van Driel
authors.forename: Pernette J
authors.initials: PJ
authors.lastname: Verschure
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D006570:Heterochromatin / Q000378:metabolism* / Q000648:ultrastructure; D006657:Histones / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000378:metabolism; D008745:Methylation; D051379:Mice; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C000715593:CBX1 protein, human; C000715594:CBX5 protein, human; C453799:Cbx3 protein, mouse; D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D006657:Histones; D007211:Indoles; D011994:Recombinant Proteins; D000090266:Chromobox Protein Homolog 5; C007293:DAPI