Abstract
Members of the heterochromatin protein 1 (HP1) family are silencing nonhistone proteins. Here, we show that in P19 embryonal carcinoma (EC) nuclei, HP1 alpha, beta, and gamma form homo- and heteromers associated with nucleosomal core histones. In vitro, all three HP1s bind to tailed and tailless nucleosomes and specifically interact with the histone-fold of histone H3. Furthermore, HP1alpha interacts with the linker histone H1. HP1alpha binds to H3 and H1 through its chromodomain (CD) and hinge region, respectively. Interestingly, the Polycomb (Pc1/M33) CD also interacts with H3, and HP1alpha and Pc1/M33 binding to H3 is severely impaired by CD mutations known to abrogate HP1 and Polycomb silencing in Drosophila. These results define a novel function for the conserved CD and suggest that HP1 self-association and histone binding may play a crucial role in HP1-mediated heterochromatin assembly.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Animals
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Binding Sites / physiology
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Chromobox Protein Homolog 5
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Chromosomal Proteins, Non-Histone / chemistry
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Chromosomal Proteins, Non-Histone / genetics
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Chromosomal Proteins, Non-Histone / metabolism*
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Conserved Sequence
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Drosophila
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Embryonal Carcinoma Stem Cells
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Epitopes / genetics
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Heterochromatin / genetics
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Heterochromatin / metabolism*
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Histones / chemistry
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Histones / genetics
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Histones / metabolism*
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In Vitro Techniques
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Mammals
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Mice
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Molecular Sequence Data
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Mutagenesis / physiology
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Neoplastic Stem Cells
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Nucleosomes / genetics
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Nucleosomes / metabolism
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Oligopeptides
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Peptides / genetics
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Polycomb Repressive Complex 1
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Polycomb-Group Proteins
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Protein Structure, Tertiary
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
Substances
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CBX5 protein, human
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Cbx2 protein, mouse
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Chromosomal Proteins, Non-Histone
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Epitopes
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Heterochromatin
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Histones
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Nucleosomes
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Oligopeptides
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Peptides
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Polycomb-Group Proteins
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Repressor Proteins
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Chromobox Protein Homolog 5
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FLAG peptide
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Polycomb Repressive Complex 1