|Entry||Database: EMDB / ID: EMD-3925|
|Title||Nucleosome breathing : Class 9|
|Biological species||Xenopus laevis (African clawed frog)|
|Method||single particle reconstruction / cryo EM / Resolution: 8.3 Å|
|Authors||Halic M / Bilokapic S|
|Citation||Journal: Nat Struct Mol Biol / Year: 2018|
Title: Histone octamer rearranges to adapt to DNA unwrapping.
Authors: Silvija Bilokapic / Mike Strauss / Mario Halic /
Abstract: Nucleosomes, the basic units of chromatin, package and regulate expression of eukaryotic genomes. Although the structure of the intact nucleosome is well characterized, little is known about ...Nucleosomes, the basic units of chromatin, package and regulate expression of eukaryotic genomes. Although the structure of the intact nucleosome is well characterized, little is known about structures of partially unwrapped, transient intermediates. In this study, we present nine cryo-EM structures of distinct conformations of nucleosome and subnucleosome particles. These structures show that initial DNA breathing induces conformational changes in the histone octamer, particularly in histone H3, that propagate through the nucleosome and prevent symmetrical DNA opening. Rearrangements in the H2A-H2B dimer strengthen interaction with the unwrapping DNA and promote nucleosome stability. In agreement with this, cross-linked H2A-H2B that cannot accommodate unwrapping of the DNA is not stably maintained in the nucleosome. H2A-H2B release and DNA unwrapping occur simultaneously, indicating that DNA is essential in stabilizing the dimer in the nucleosome. Our structures reveal intrinsic nucleosomal plasticity that is required for nucleosome stability and might be exploited by extrinsic protein factors.
|Validation Report||Summary, Full report, XML, About validation report|
|Structure viewer||EM map: |
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|File||Download / File: emd_3925.map.gz / Format: CCP4 / Size: 18.1 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)|
|Projections & slices|
Images are generated by Spider.
|Voxel size||X=Y=Z: 1.4 Å|
|Symmetry||Space group: 1|
CCP4 map header:
|Entire||Name: Nucleosome / Number of components: 1|
-Component #1: protein, Nucleosome
|Protein||Name: Nucleosome / Recombinant expression: No|
|Mass||Theoretical: 200 kDa|
|Source||Species: Xenopus laevis (African clawed frog)|
|Source (engineered)||Expression System: Escherichia coli (E. coli)|
|Specimen||Specimen state: Particle / Method: cryo EM|
|Sample solution||pH: 7.4|
|Vitrification||Cryogen name: ETHANE|
-Electron microscopy imaging
|Imaging||Microscope: FEI TITAN|
|Electron gun||Electron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Electron dose: 100 e/Å2 / Illumination mode: FLOOD BEAM|
|Lens||Imaging mode: BRIGHT FIELD|
|Specimen Holder||Model: OTHER|
|Camera||Detector: FEI FALCON II (4k x 4k)|
|Processing||Method: single particle reconstruction / Applied symmetry: C1 (asymmetric) / Number of projections: 9000|
|3D reconstruction||Software: RELION / Resolution: 8.3 Å / Resolution method: FSC 0.143 CUT-OFF|
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