ATP-dependent histone octamer mobilization and histone deacetylation mediated by the Mi-2 chromatin remodeling complex

The Mi-2 complex has been implicated in chromatin remodeling and transcript ional repression associated with histone deacetylation. Here, we use a puri fied Mi-2 complex containing six components, Mi-2, Mta 1-like, p66, RbAp48, RPD3, and MBD3, to investigate the capacity of this complex to destabilize histone-DNA interactions and deacetylate core histones. The Mi-2 complex h as ATPase activity that is stimulated by nucleosomes but not by free histon es or DNA. This nucleosomal ATPase is relatively inefficient, yet is essent ial to facilitate both translational movement of histone octamers relative to DNA and the efficient deacetylation of the core histones within a mononu cleosome. Surprisingly, ATPase activity had no effect on deacetylation of n ucleosomal arrays.