Activated RSC–Nucleosome Complex and Persistently Altered Form of the Nucleosome

RSC, an abundant, essential chromatin-remodeling complex, related to SWI/SNF complex, binds nucleosomes and naked DNA with comparable affinities, as shown by gel shift analysis. The RSC-nucleosome complex is converted in the presence of ATP to a slower migrating form. This activated complex exhibits greatly increased susceptibility to endo- and exonucleases but retains a full complement of histones. Activation persists in the absence of ATP, and on removal of RSC, the nucleosome is released in an altered form, with a diminished electrophoretic mobility, greater sedimentation rate, and marked instability at elevated ionic strength. The reaction is reversible in the presence of RSC and ATP, with conversion of the altered form back to the nucleosome.