Molecular Cell
Volume 7, Issue 4, April 2001, Pages 729-739
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Research article
Heterochromatin Formation in Mammalian Cells: Interaction between Histones and HP1 Proteins

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Abstract

Members of the heterochromatin protein 1 (HP1) family are silencing nonhistone proteins. Here, we show that in P19 embryonal carcinoma (EC) nuclei, HP1 α, β, and γ 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, HP1α interacts with the linker histone H1. HP1α binds to H3 and H1 through its chromodomain (CD) and hinge region, respectively. Interestingly, the Polycomb (Pc1/M33) CD also interacts with H3, and HP1α 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.

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Present address: Instituto de Neurociencias, Universidad Miguel Hernández–CSIC, Centra Valencia Km 87, 03550 San Juan (Alicante), Spain.