We have developed dominant negative forms of the Brg1, INO80, Snf2h, and CHD4 human chromatin remodeling proteins, and have developed individual cell lines expressing these dominant negative activities under inducible (tetracycline) regulation. We have characterized the biochemical acitivity of these mutant complexes, and shown that they are each defective in nucleosome remodeling activity. We are studying the potential role of these remodeling systems in the action of nuclear receptors at specific sites of remodeling genome wide. We have discovered that multiple remodeling complexes funciton at almost all regulatory elements in the murine genome.