Nucleosome movement by CHRAC and ISWI without disruption or trans-displacement of the histone octamer

The chromatin accessibility complex (CHRAC) belongs to the class of nucleos ome remodeling factors that increase the accessibility of nucleosomal DNA i n an ATP-dependent manner. We found that CHRAC induces movements of intact histone octamers to neighboring DNA segments without facilitating their dis placement to competing DNA or histone chaperones in trans. CHRAC-induced en ergy-dependent nucleosome sliding may, in principle, explain nucleosome rem odeling, nucleosome positioning, and nucleosome spacing reactions known to be catalyzed by CHRAC. The catalytic core of CHRAC, the ATPase ISWI, also m obilized nucleosomes at the expense of energy. However, the directionality of the CHRAC- and ISWI-induced nucleosome movements differed drastically, i ndicating that the geometry of the native complex modulates the activity of its catalytic core.