Mitotic phosphorylation of HP1α regulates its cell cycle-dependent chromatin binding
Mitotic phosphorylation of HP1α regulates its cell cycle-dependent chromatin binding
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HP1α 有丝分裂磷酸化调节其细胞周期依赖性染色质结合
DOI：
10.1093/jb/mvy117
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Jun-ichi Nakayama
中科院分区：
文献类型：
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作者：
Gohei Nishibuchi;Shinichi Machida;Reiko Nakagawa;Yuriko Yoshimura;Kyoko Hiragami-Hamada;Yusuke Abe;Hitoshi Kurumizaka;Hideaki Tagami;Jun-ichi Nakayama
异染色质蛋白 1 (HP1) 是一种进化上保守的染色体蛋白，在异染色质介导的基因沉默中发挥着至关重要的作用。我们之前表明，哺乳动物 HP1α 在其 N 端丝氨酸残基上被酪蛋白激酶 II (CK2) 组成型磷酸化，并且这种磷酸化增强了 HP1α 对含有赖氨酸 9-甲基化组蛋白 H3 (H3K9me) 的核小体的结合特异性。尽管十多年前就报道了有丝分裂期间存在额外的 HP1α 磷酸化，但其生物学意义仍然很大程度上难以捉摸。在这里，我们发现有丝分裂特异性的 HP1α 磷酸化影响 HP1α 结合染色质的能力。通过生化和突变分析，我们发现 HP1α 的有丝分裂磷酸化位于其铰链区，并受到 Aurora B 激酶和丝氨酸/苏氨酸磷酸酶的可逆调节。此外，染色质分级分离和电泳迁移率变动分析表明，铰链区磷酸化的 HP1α 优先从有丝分裂染色质解离，并表现出 DNA 结合活性降低。尽管 HP1 的有丝分裂行为之前与 H3 丝氨酸 10 磷酸化有关，H3 丝氨酸 10 磷酸化会阻止 HP1 染色质结构域与 H3K9me3 的结合，但我们的研究结果表明 HP1α 铰链区的有丝分裂磷酸化也有助于 HP1α 与有丝分裂染色质关联的变化。
Heterochromatin protein 1 (HP1) is an evolutionarily conserved chromosomal protein that plays a crucial role in heterochromatin-mediated gene silencing. We previously showed that mammalian HP1α is constitutively phosphorylated at its N-terminal serine residues by casein kinase II (CK2), and that this phosphorylation enhances HP1α’s binding specificity for nucleosomes containing lysine 9-methylated histone H3 (H3K9me). Although the presence of additional HP1α phosphorylation during mitosis was reported more than a decade ago, its biological significance remains largely elusive. Here we found that mitosis-specific HP1α phosphorylation affected HP1α’s ability to bind chromatin. Using biochemical and mutational analyses, we showed that HP1α’s mitotic phosphorylation was located in its hinge region and was reversibly regulated by Aurora B kinase and serine/threonine phosphatases. In addition, chromatin fractionation and electrophoretic mobility shift assays revealed that hinge region-phosphorylated HP1α was preferentially dissociated from mitotic chromatin and exhibited a reduced DNA-binding activity. Although HP1’s mitotic behaviour was previously linked to H3 serine 10 phosphorylation, which blocks the binding of HP1’s chromodomain to H3K9me3, our findings suggest that mitotic phosphorylation in HP1α’s hinge region also contributes to changes in HP1α’s association with mitotic chromatin.