Chester Beatty Laboratories, Institute of Cancer Research, London SW3 6JB, United Kingdom.
Proc Natl Acad Sci U S A. 2012 Dec 18;109(51):20883-8. doi: 10.1073/pnas.1214735109. Epub 2012 Dec 3.
Actin-related protein Arp8 is a component of the INO80 chromatin remodeling complex. Yeast Arp8 (yArp8) comprises two domains: a 25-KDa N-terminal domain, found only in yeast, and a 75-KDa C-terminal domain (yArp8CTD) that contains the actin fold and is conserved across other species. The crystal structure shows that yArp8CTD contains three insertions within the actin core. Using a combination of biochemistry and EM, we show that Arp8 forms a complex with nucleosomes, and that the principal interactions are via the H3 and H4 histones, mediated through one of the yArp8 insertions. We show that recombinant yArp8 exists in monomeric and dimeric states, but the dimer is the biologically relevant form required for stable interactions with histones that exploits the twofold symmetry of the nucleosome core. Taken together, these data provide unique insight into the stoichiometry, architecture, and molecular interactions between components of the INO80 remodeling complex and nucleosomes, providing a first step toward building up the structure of the complex.
肌动蛋白相关蛋白 Arp8 是 INO80 染色质重塑复合物的一个组成部分。酵母 Arp8（yArp8）包含两个结构域：一个 25kDa 的 N 端结构域，仅在酵母中发现，以及一个包含肌动蛋白折叠结构域的 75kDa 的 C 端结构域（yArp8CTD），该结构域在其他物种中是保守的。晶体结构显示 yArp8CTD 在肌动蛋白核心内包含三个插入序列。我们使用生物化学和 EM 的组合方法表明，Arp8 与核小体形成复合物，主要的相互作用是通过 H3 和 H4 组蛋白介导的，通过 yArp8 的一个插入序列进行。我们表明，重组 yArp8 存在单体和二聚体状态，但二聚体是与核小体核心的两倍对称性利用稳定相互作用的生物相关形式，需要与组蛋白稳定相互作用。综上所述，这些数据提供了 INO80 重塑复合物和核小体组件之间的化学计量、结构和分子相互作用的独特见解，为构建复合物的结构提供了第一步。
