CENP-C unwraps the human CENP-A nucleosome through the H2A C-terminal tail
CENP-C unwraps the human CENP-A nucleosome through the H2A C-terminal tail
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DOI：
10.15252/embr.201948913
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发表时间：
2019-09-02
期刊：
影响因子：
7.7
通讯作者：
Sekulic, Nikolina
中科院分区：
文献类型：
--
作者：
Ali-Ahmad, Ahmad;Bilokapic, Silvija;Sekulic, Nikolina
着丝粒是由含有组蛋白H3变异体CENP-A的核小体在表观遗传学上定义的，在此基础上建立了结构性着丝粒相关蛋白质网络(CCAN)。CENP-C被认为是CCAN的中心组织者。我们对人CENP-A核小体的结构提供了新的分子见解，分离并与CENP-C中心区(CENP-C-CR)复合，CENP-C-CR是人CENP-C的主要CENP-A结合模块。我们证实，CENP-A的短αN螺旋促进了核小体末端的DNA灵活性，而不依赖于它包裹的序列。此外，我们发现，在体外，人CENP-C的两个区域(CENP-C-CR和CENP-C-Motif)都与CENP-A核小体特异结合。我们发现CENP-C-CR由于由CENP-A(V532)和CENP-A(V533)组成的延伸疏水区域而具有高亲和力。重要的是，我们确定了CENP-C结合时CENP-A核小体内的两个关键构象变化。首先，通过H_2A C-末端尾部的不稳定，CENP-A核小体的松散DNA包裹进一步加剧。第二，CENP-C-CR使H4的N端末端刚性化为有利于H4(K20)单甲基化的构象，这对功能着丝粒是必不可少的。
Centromeres are defined epigenetically by nucleosomes containing the histone H3 variant CENP-A, upon which the constitutive centromere-associated network of proteins (CCAN) is built. CENP-C is considered to be a central organizer of the CCAN. We provide new molecular insights into the structure of human CENP-A nucleosomes, in isolation and in complex with the CENP-C central region (CENP-C-CR), the main CENP-A binding module of human CENP-C. We establish that the short alpha N helix of CENP-A promotes DNA flexibility at the nucleosome ends, independently of the sequence it wraps. Furthermore, we show that, in vitro, two regions of human CENP-C (CENP-C-CR and CENP-C-motif) both bind exclusively to the CENP-A nucleosome. We find CENP-C-CR to bind with high affinity due to an extended hydrophobic area made up of CENP-A(V532) and CENP-A(V533). Importantly, we identify two key conformational changes within the CENP-A nucleosome upon CENP-C binding. First, the loose DNA wrapping of CENP-A nucleosomes is further exacerbated, through destabilization of the H2A C-terminal tail. Second, CENP-C-CR rigidifies the N-terminal tail of H4 in the conformation favoring H4(K20) monomethylation, essential for a functional centromere.