ATP-dependent reorientation on a nucleosome primes INO80 for DNA translocation.

ATP-dependent chromatin remodeling enzymes play central roles in genome regulation by mobilizing nucleosomes. All remodelers except for one, position their core ATPase at an internal nucleosome location, superhelical location (SHL) 2, and translocate DNA from this site to alter nucleosome conformation. The exception, the remodeler INO80, positions its core ATPase, Ino80, near the DNA exit/entry site, SHL -6. This major architectural difference has raised the question of whether INO80 acts by a fundamentally different mechanism from other remodelers. Here, using cryogenic electron microscopy we capture a new conformation of INO80 that is substantially enriched upon ATP hydrolysis and has Ino80 positioned at an internal nucleosomal location. Comprehensive conformational landscape analysis further uncovers an ATP hydrolysis dependent continuum of additional INO80 conformational states on a nucleosome that were not previously detected. Our studies provide compelling evidence to support a model where INO80 initially engages nucleosomes near SHL -6, followed by a dramatic ATP hydrolysis dependent ~180° reorientation around the nucleosome to place its Ino80 near SHL -2 from where DNA is translocated. INO80's unique reorientation has broad implications for understanding how ATP-dependent steps that precede nucleosome mobilization can increase the fidelity of remodeling by being responsive to nucleosomal cues.