Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science & Technology of China, Hefei, China.
CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Hefei, China.
J Mol Cell Biol. 2019 May 1;11(5):345-355. doi: 10.1093/jmcb/mjy062.
The presence and functions of nuclear actin have been controversial due to the lack of molecular mechanisms. Nuclear actin and actin-related proteins (Arps) are subunits of several chromatin remodelers, including the evolutionarily conserved INO80 chromatin-remodeling complex. Here, we present an improved cryo-EM structure of the yeast INO80 complex and the first 3D reconstruction of the INO80 actin/Arp module. The modular and subunit architecture is defined using a combination of subunit deletion analysis and published crosslinking-mass spectrometry. The functional interactions of the INO80 actin/Arp module with a nucleosome is 3D EM reconstructed in two different binding states. Nucleosomes initially bind to the Arp8 subunit and the substantial conformational changes maximize nucleosome contacts of the actin/Arp module, which could promote the bound nucleosome to be engaged onto the INO80 ATPase domain. Our findings suggest that the conserved nuclear actin/Arp module acts a conformational switch of the INO80 for nucleosome binding.
由于缺乏分子机制，核肌动蛋白的存在和功能一直存在争议。核肌动蛋白和肌动蛋白相关蛋白（Arp）是几种染色质重塑剂的亚基，包括进化上保守的 INO80 染色质重塑复合物。在这里，我们提出了一个改进的酵母 INO80 复合物的 cryo-EM 结构和 INO80 肌动蛋白/Arp 模块的第一个 3D 重建。使用亚基缺失分析和已发表的交联质谱法的组合，定义了模块化和亚基结构。INO80 肌动蛋白/Arp 模块与核小体的功能相互作用在两种不同的结合状态下进行了 3D EM 重建。核小体最初与 Arp8 亚基结合，并且构象发生显著变化，从而使肌动蛋白/Arp 模块与核小体的接触最大化，这可能促进结合的核小体与 INO80 ATP 酶结构域结合。我们的发现表明，保守的核肌动蛋白/Arp 模块是 INO80 与核小体结合的构象开关。
