ATP-dependent remodeling of chromatin condensates reveals distinct mesoscale outcomes.

Abstract

Adenosine triphosphate (ATP)-dependent chromatin remodeling enzymes mobilize nucleosomes, but how such mobilization affects chromatin condensation is unclear. We investigate effects of two major remodelers, ACF and RSC, using chromatin condensates and single-molecule footprinting. We find that both remodelers inhibit the formation of condensed chromatin. However, the remodelers have distinct effects on preformed chromatin condensates. ACF spaces nucleosomes without decondensing the chromatin, explaining how ACF maintains nucleosome organization in transcriptionally repressed genomic regions. By contrast, RSC catalyzes ATP-dependent decondensation of chromatin. RSC also drives micron-scale movements of entire chromatin condensates. These additional activities of RSC may contribute to its central role in transcription. The biological importance of remodelers may thus reflect both their effects on nucleosome mobilization and the corresponding consequences on chromatin dynamics at the mesoscale.