N-terminal phosphorylation of HP1α increases its nucleosome-binding specificity

Gohei Nishibuchi, Shinichi Machida, Akihisa Osakabe, Hiromu Murakoshi, Kyoko Hiragami-Hamada, Reiko Nakagawa, Wolfgang Fischle, Yoshifumi Nishimura, Hitoshi Kurumizaka, Hideaki Tagami, Jun ichi Nakayama

    Research output: Contribution to journalArticle

    27 Citations (Scopus)

    Abstract

    Heterochromatin protein 1 (HP1) is an evolutionarily conserved chromosomal protein that binds to lysine 9-methylated histone H3 (H3K9me), a hallmark of heterochromatin. Although HP1 phosphorylation has been described in several organisms, the biological implications of this modification remain largely elusive. Here we show that HP1's phosphorylation has a critical effect on its nucleosome binding properties. By in vitro phosphorylation assays and conventional chromatography, we demonstrated that casein kinase II (CK2) is the kinase primarily responsible for phosphorylating the N-terminus of human HP1α. Pull-down assays using in vitro-reconstituted nucleosomes showed that unmodified HP1α bound H3K9-methylated and H3K9-unmethylated nucleosomes with comparable affinity, whereas CK2-phosphorylated HP1α showed a high specificity for H3K9me3-modified nucleosomes. Electrophoretic mobility shift assays showed that CK2-mediated phosphorylation diminished HP1α's intrinsic DNA binding, which contributed to its H3K9me-independent nucleosome binding. CK2-mediated phosphorylation had a similar effect on the nucleosome-binding specificity of fly HP1a and S. pombe Swi6. These results suggested that HP1 phosphorylation has an evolutionarily conserved role in HP1's recognition of H3K9me-marked nucleosomes.

    Original languageEnglish
    Pages (from-to)12498-12511
    Number of pages14
    JournalNucleic Acids Research
    Volume42
    Issue number20
    DOIs
    Publication statusPublished - 2014 Nov 10

    ASJC Scopus subject areas

    • Medicine(all)

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