Identification of a rapidly formed nonnucleosomal histone-DNA intermediate that is converted into chromatin by ACF.

Sharon E Torigoe, Debra L Urwin, Haruhiko Ishii, Douglas E Smith, James T Kadonaga

Section of Molecular Biology, University of California, San Diego, La Jolla, CA 92093-0347, USA.

Molecular cell 2011 Aug 19

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Chromatin assembly involves the combined action of histone chaperones and ATP-dependent motor proteins. Here, we investigate the mechanism of nucleosome assembly with a purified chromatin assembly system containing the histone chaperone NAP1 and the ATP-dependent motor protein ACF. These studies revealed the rapid formation of a stable nonnucleosomal histone-DNA intermediate that is converted into canonical nucleosomes by ACF. The histone-DNA intermediate does not supercoil DNA like a canonical nucleosome, but has a nucleosome-like appearance by atomic force microscopy. This intermediate contains all four core histones, lacks NAP1, and is formed by the initial deposition of histones H3-H4. Conversion of the intermediate into histone H1-containing chromatin results in increased resistance to micrococcal nuclease digestion. These findings suggest that the histone-DNA intermediate corresponds to nascent nucleosome-like structures, such as those observed at DNA replication forks. Related complexes might be formed during other chromatin-directed processes such as transcription, DNA repair, and histone exchange. Copyright © 2011 Elsevier Inc. All rights reserved.

Citation

Sharon E Torigoe, Debra L Urwin, Haruhiko Ishii, Douglas E Smith, James T Kadonaga. Identification of a rapidly formed nonnucleosomal histone-DNA intermediate that is converted into chromatin by ACF. Molecular cell. 2011 Aug 19;43(4):638-48