Genome-Wide Kinetics of Nucleosome Turnover Determined by Metabolic Labeling of Histones

Abstract

Everything Changes Nucleosomes package DNA, and their assembly and disassembly regulate access to the genome. The ability to follow these changes is limited to steady-state methods in higher eukaryotes, although direct kinetic analyses are available in yeast. To address this deficiency, Deal et al. (p. 1161 ) developed a general method for following the genome-wide dynamics of nucleosome assembly and disassembly. High levels of nucleosome turnover were observed across gene bodies and at the sites of epigenetic regulatory elements in fruit fly tissue culture cells. Nucleosomes were replaced multiple times during each 20-hour cell cycle, suggesting that histone modifications themselves are unlikely to transmit epigenetic information. Furthermore, analysis of replication origins indicates that they are determined by chromatin dynamics and not by sequence features.