title: Polycomb group protein-associated chromatin is reproduced in post-mitotic G1 phase and is required for S phase progression.
abstract: Polycomb group (PcG) proteins form two distinct complexes, PRC1 and PRC2, to regulate developmental target genes by maintaining the epigenetic state in cells. PRC2 methylates histone H3 at lysine 27 (H3K27), and PRC1 then recognizes methyl-H3K27 to form repressive chromatin. However, it remains unknown how PcG proteins maintain stable and plastic chromatin during cell division. Here we report that PcG-associated chromatin is reproduced in the G(1) phase in post-mitotic cells and is required for subsequent S phase progression. In dividing cells, H3K27 trimethylation (H3K27Me(3)) marked mitotic chromosome arms where PRC2 (Suz12 and Ezh2) co-existed, whereas PRC1 (Bmi1 and Pc2) appeared in distinct foci in the pericentromeric regions. As each PRC complex was increasingly assembled from mitosis to G(1) phase, PRC1 formed H3K27Me(3)-based chromatin intensively during middle and late G(1) phase; this chromatin was highly resistant to in situ nuclease treatment. Thus, the transition from mitosis to G(1) phase is crucial for PcG-mediated chromatin inheritance. Knockdown of Suz12 markedly reduced the amount of H3K27Me(3) on mitotic chromosomes, and as a consequence, PRC1 foci were not fully transmitted to post-mitotic daughter cells. S phase progression was markedly delayed in these Suz12-knockdown cells. The fact that PcG-associated chromatin is reproduced during post-mitotic G(1) phase suggests the possibility that PcG proteins enable their target chromatin to be remodeled in response to stimuli in the G(1) phase.
authors.affiliation: Department of Regeneration Medicine, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Aoto
authors.forename: Noriko
authors.initials: N
authors.lastname: Saitoh
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Sakamoto
authors.forename: Sugiko
authors.initials: S
authors.lastname: Watanabe
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Nakao
mesh_terms: D000818:Animals; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000071221:Enhancer of Zeste Homolog 2 Protein; D044127:Epigenesis, Genetic / Q000502:physiology; D016193:G1 Phase / Q000502:physiology*; D006367:HeLa Cells; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008025:Ligases; D008745:Methylation; D051379:Mice; D008938:Mitosis / Q000502:physiology; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D041681:NIH 3T3 Cells; D063151:Polycomb Repressive Complex 2; D063146:Polycomb-Group Proteins; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D006657:Histones; D046912:Multiprotein Complexes; D063146:Polycomb-Group Proteins; D011506:Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C498409:EZH2 protein, human; D000071221:Enhancer of Zeste Homolog 2 Protein; C498410:Ezh2 protein, mouse; D011495:Histone-Lysine N-Methyltransferase; D063151:Polycomb Repressive Complex 2; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C570427:CBX4 protein, human