Structure of an H1-Bound 6-Nucleosome Array Reveals an Untwisted Two-Start Chromatin Fiber Conformation
Language English Country United States Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
30392928
DOI
10.1016/j.molcel.2018.09.027
PII: S1097-2765(18)30798-6
Knihovny.cz E-resources
- Keywords
- 30-nm fiber, chromatin, cryo-EM, crystallography, histone H1, linker histone, nucleosome array,
- MeSH
- DNA chemistry genetics metabolism MeSH
- Cryoelectron Microscopy MeSH
- Escherichia coli genetics metabolism MeSH
- Gene Expression MeSH
- Genetic Vectors chemistry metabolism MeSH
- Histones chemistry genetics metabolism MeSH
- Hydroxyl Radical chemistry MeSH
- Protein Interaction Domains and Motifs MeSH
- Cloning, Molecular MeSH
- Protein Conformation, alpha-Helical MeSH
- Protein Conformation, beta-Strand MeSH
- Crystallography, X-Ray MeSH
- Humans MeSH
- Models, Molecular MeSH
- Protein Multimerization MeSH
- Nucleosomes chemistry metabolism ultrastructure MeSH
- Osmolar Concentration MeSH
- Nucleosome Assembly Protein 1 chemistry genetics metabolism MeSH
- Recombinant Proteins chemistry genetics metabolism MeSH
- Protein Binding MeSH
- Binding Sites MeSH
- Xenopus laevis MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- DNA MeSH
- Histones MeSH
- Hydroxyl Radical MeSH
- Nucleosomes MeSH
- Nucleosome Assembly Protein 1 MeSH
- Recombinant Proteins MeSH
Chromatin adopts a diversity of regular and irregular fiber structures in vitro and in vivo. However, how an array of nucleosomes folds into and switches between different fiber conformations is poorly understood. We report the 9.7 Å resolution crystal structure of a 6-nucleosome array bound to linker histone H1 determined under ionic conditions that favor incomplete chromatin condensation. The structure reveals a flat two-start helix with uniform nucleosomal stacking interfaces and a nucleosome packing density that is only half that of a twisted 30-nm fiber. Hydroxyl radical footprinting indicates that H1 binds the array in an on-dyad configuration resembling that observed for mononucleosomes. Biophysical, cryo-EM, and crosslinking data validate the crystal structure and reveal that a minor change in ionic environment shifts the conformational landscape to a more compact, twisted form. These findings provide insights into the structural plasticity of chromatin and suggest a possible assembly pathway for a 30-nm fiber.
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