Cryo-EM study of the chromatin fiber reveals a double helix twisted by tetranucleosomal units.
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.
National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Feng
F
Song
Ping
P
Chen
Dapeng
D
Sun
Mingzhu
M
Wang
Liping
L
Dong
Dan
D
Liang
Rui-Ming
RM
Xu
Ping
P
Zhu
Guohong
G
Li
D000595:Amino Acid Sequence; D000818:Animals; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure*; D020285:Cryoelectron Microscopy; D004247:DNA / Q000737:chemistry / Q000648:ultrastructure*; D006657:Histones / Q000737:chemistry* / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000648:ultrastructure*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D029867:Xenopus Proteins / Q000737:chemistry; D014982:Xenopus laevis
D002843:Chromatin; D006657:Histones; D009707:Nucleosomes; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D004247:DNA