Heterochromatin formation in mammalian cells: interaction between histones and HP1 proteins.

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.
Mesh Terms:
Amino Acid Sequence, Animals, Binding Sites, Chromosomal Proteins, Non-Histone, Conserved Sequence, Drosophila, Embryonal Carcinoma Stem Cells, Epitopes, Heterochromatin, Histones, Mammals, Mice, Molecular Sequence Data, Mutagenesis, Neoplastic Stem Cells, Nucleosomes, Peptides, Protein Structure, Tertiary, Repressor Proteins
Mol. Cell
Date: Apr. 01, 2001
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