Strohner, R., Wachsmuth, M., Dachauer, K., Mazurkiewicz, J., Hochstatter, J., Rippe, K., Langst, G. (2005). A 'loop recapture' mechanism for ACF-dependent nucleosome remodeling.  Nat. Struct. Mol. Biol. 12(8): 683--690.

FBrf0191295

Research paper

The ATPase ISWI is the molecular motor of several nucleosome remodeling complexes including ACF. We analyzed the ACF-nucleosome interactions and determined the characteristics of ACF-dependent nucleosome remodeling. In contrast to ISWI, ACF interacts symmetrically with DNA entry sites of the nucleosome. Two-color fluorescence cross-correlation spectroscopy measurements show that ACF can bind four DNA duplexes simultaneously in a complex that contains two Acf1 and ISWI molecules. Using bead-bound nucleosomal substrates, nucleosome movement by mechanisms involving DNA twisting was excluded. Furthermore, an ACF-dependent local detachment of DNA from the nucleosome was demonstrated in a novel assay based on the preferred intercalation of ethidium bromide to free DNA. The findings suggest a loop recapture mechanism in which ACF introduces a DNA loop at the nucleosomal entry site that propagates over the histone octamer surface and leads to nucleosome repositioning.