Figure 8. Nucleosome remodeling at promoters.

Model for nucleosome remodeling cycle at a gene promoter region targeted by RSC, SWI/SNF, INO80, and ISW2. The promoter region transitions between remodeler-occupied [solid arrow] and remodeler-vacant [dashed arrow] states, and their mean durations are indicated. After association with the NDR, remodelers undergo 1-D diffusion on chromatin facilitated by ATP binding, resulting in higher chromatin-associated mobility. Upon engaging a nucleosome substrate [e.g. the +1 nucleosome], RSC or SWI/SNF uses the energy of ATP hydrolysis to ‘push’ the nucleosome away from the NDR and INO80 or ISW2 to ‘pull’ the nucleosome into the NDR. ATP hydrolysis facilitates remodeler dissociation, and the promoter region becomes vacant for other factor interactions. The order of remodeler visitation is arbitrary, and simultaneous co-occupancy within the NDR can occur (see text for details).