National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Science. 2014 Apr 25;344(6182):376-80. doi: 10.1126/science.1251413.
The hierarchical packaging of eukaryotic chromatin plays a central role in transcriptional regulation and other DNA-related biological processes. Here, we report the 11-angstrom-resolution cryogenic electron microscopy (cryo-EM) structures of 30-nanometer chromatin fibers reconstituted in the presence of linker histone H1 and with different nucleosome repeat lengths. The structures show a histone H1-dependent left-handed twist of the repeating tetranucleosomal structural units, within which the four nucleosomes zigzag back and forth with a straight linker DNA. The asymmetric binding and the location of histone H1 in chromatin play a role in the formation of the 30-nanometer fiber. Our results provide mechanistic insights into how nucleosomes compact into higher-order chromatin fibers.
真核染色质的层级包装在转录调控和其他与 DNA 相关的生物过程中起着核心作用。在这里，我们报道了在连接组蛋白 H1 存在下重新组装的具有不同核小体重复长度的 30 纳米染色质纤维的 11 埃分辨率低温电子显微镜 (cryo-EM) 结构。这些结构显示出组蛋白 H1 依赖性的重复四联体结构单元的左手扭曲，其中四个核小体以直连接 DNA 来回曲折。不对称结合和组蛋白 H1 在染色质中的位置在 30 纳米纤维的形成中起作用。我们的结果提供了关于核小体如何压缩成更高阶染色质纤维的机制见解。
