Nucleosome sliding mechanisms: new twists in a looped history

Nucleosomes, the basic organizational units of chromatin, package and regulate eukaryotic genomes. ATP-dependent nucleosome-remodeling factors endow chromatin with structural flexibility by promoting assembly or disruption of nucleosomes and the exchange of histone variants. Furthermore, most remodeling factors induce nucleosome movements through sliding of histone octamers on DNA. We summarize recent progress toward unraveling the basic nucleosome sliding mechanism and the interplay of the remodelers' DNA translocases with accessory domains. Such domains optimize and regulate the basic sliding reaction and exploit sliding to achieve diverse structural effects, such as nucleosome positioning or eviction, or the regular spacing of nucleosomes in chromatin.