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Replacement of histone H3 with CENP-A directs global nucleosome array condensation and loosening of nucleosome superhelical termini.

Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 09/2011; 108(40):16588-93. DOI: 10.1073/pnas.1113621108
Source: PubMed

ABSTRACT Centromere protein A (CENP-A) is a histone H3 variant that marks centromere location on the chromosome. To study the subunit structure and folding of human CENP-A-containing chromatin, we generated a set of nucleosomal arrays with canonical core histones and another set with CENP-A substituted for H3. At the level of quaternary structure and assembly, we find that CENP-A arrays are composed of octameric nucleosomes that assemble in a stepwise mechanism, recapitulating conventional array assembly with canonical histones. At intermediate structural resolution, we find that CENP-A-containing arrays are globally condensed relative to arrays with the canonical histones. At high structural resolution, using hydrogen-deuterium exchange coupled to mass spectrometry (H/DX-MS), we find that the DNA superhelical termini within each nucleosome are loosely connected to CENP-A, and we identify the key amino acid substitution that is largely responsible for this behavior. Also the C terminus of histone H2A undergoes rapid hydrogen exchange relative to canonical arrays and does so in a manner that is independent of nucleosomal array folding. These findings have implications for understanding CENP-A-containing nucleosome structure and higher-order chromatin folding at the centromere.

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Available from: Walter Englander, Apr 17, 2015
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