Cryo-EM Study of the Chromatin Fiber Reveals a Double Helix Twisted by Tetranucleosomal Units

作者：Feng Song, Ping Chen, Dapeng Sun, Mingzhu Wang, Liping Dong, Dan Liang, Rui-Ming Xu, Ping Zhu, Guohong Li · 发表于：Science · 年份：2014 · DOI：10.1126/science.1251413 · 被引用次数：660 · 研究领域：Genomics and Chromatin Dynamics、RNA and protein synthesis mechanisms、RNA modifications and cancer

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.