Structure of the Human Core Centromeric Nucleosome Complex
Structure of the Human Core Centromeric Nucleosome Complex
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DOI：
10.1016/j.cub.2019.06.062
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发表时间：
2019-08-19
期刊：
影响因子：
9.2
通讯作者：
Black, Ben E.
中科院分区：
文献类型：
--
作者：
Allu, Praveen Kumar;Dawicki-McKenna, Jennine M.;Black, Ben E.
着丝粒核小体位于染色体和动粒的界面，在有丝分裂中连接到纺锤体微管。核心着丝粒核小体复合物（CCNC）含有组蛋白H3变体CENP-A及其结合蛋白CENP-C（通过其中心结构域; CD）和CENP-N（通过其N-末端结构域; NT）。CENP-C可以通过两个结构域接合核小体：CD和CENP-C基序（CM）。CENP-C-CD由于其对CENP-A核小体的高特异性和在着丝粒处稳定CENP-A的能力而成为CCNC的一部分。CENP-C-CM被认为与相邻的核小体接合，所述核小体包含常规H3或CENP-A，并且报道了包含两个拷贝的CENP-C-CM的核小体复合物的晶体结构。最近的结构，含有一个单一拷贝的CENP-N-NT结合的CENP-A核小体在CENP-C的情况下，报告。在这里，我们发现，一个拷贝的CENP-N是丢失的每两个拷贝的CENP-C着丝粒染色质之前动粒形成。我们提出了对称和不对称形式的CCNC的CENP-N化学计量的变化的结构。我们的结构解释了CENP-C的中心结构域如何实现其对CENP-A核小体的高特异性，以及CENP-C和CENP-N如何夹在组蛋白H4尾之间。在我们的结构中的自然着丝粒DNA路径对应于CCNC组装的对称表面，偏离了使用人工序列在先前结构中观察到的。在有丝分裂，我们建议，CCNC的不对称适应其不对称连接在染色体/动粒接口。
Centromeric nucleosomes are at the interface of the chromosome and the kinetochore that connects to spindle microtubules in mitosis. The core centromeric nucleosome complex (CCNC) harbors the histone H3 variant, CENP-A, and its binding proteins, CENP-C (through its central domain; CD) and CENP-N (through its N-terminal domain; NT). CENP-C can engage nucleosomes through two domains: the CD and the CENP-C motif (CM). CENP-C-CD is part of the CCNC by virtue of its high specificity for CENP-A nucleosomes and ability to stabilize CENP-A at the centromere. CENP-C-CM is thought to engage a neighboring nucleosome, either one containing conventional H3 or CENP-A, and a crystal structure of a nucleosome complex containing two copies of CENP-C-CM was reported. Recent structures containing a single copy of CENP-N-NT bound to the CENP-A nucleosome in the absence of CENP-C were reported. Here, we find that one copy of CENP-N is lost for every two copies of CENP-C on centromeric chromatin just prior to kinetochore formation. We present the structures of symmetric and asymmetric forms of the CCNC that vary in CENP-N stoichiometry. Our structures explain how the central domain of CENP-C achieves its high specificity for CENP-A nucleosomes and how CENP-C and CENP-N sandwich the histone H4 tail. The natural centromeric DNA path in our structures corresponds to symmetric surfaces for CCNC assembly, deviating from what is observed in prior structures using artificial sequences. At mitosis, we propose that CCNC asymmetry accommodates its asymmetric connections at the chromosome/kinetochore interface.