6esi
Nucleosome breathing : Class 4
Structural highlights
FunctionH32_XENLA Core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. Publication Abstract from PubMedNucleosomes, 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. Histone octamer rearranges to adapt to DNA unwrapping.,Bilokapic S, Strauss M, Halic M Nat Struct Mol Biol. 2018 Jan;25(1):101-108. doi: 10.1038/s41594-017-0005-5. Epub, 2017 Dec 11. PMID:29323273[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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