purification and characterization of msin3acontaining brg1 and hbrm chromatin remodeling complexes alteration of nucleosomes by atpdependent remodeling complexes represents a critical step in the regulation of transcription the human swisnf hswisnf family is composed of complexes that contain either brg1 or hbrm as the central atpase however these separate complexes have not been compared functionally here we describe the establishment of cell lines that express epitopetagged brg1 and hbrm and a characterization of the complexes associated with these two atpases we show that brg1 fractionates into two complexes that differ in activity and subunit composition whereas hbrm is found in one complex with lower activity than the brg1 complexes these three complexes can remodel nucleosomal arrays increase restriction enzyme accessibility and hydrolyze atp in a dnadependent manner the three complexes differ markedly in their ability to remodel mononucleosomal core particles we also show that the hbrm complex and one of the brg1 complexes contain components of the mammalian sin3 msin3 complex in addition we have found that brg1 hbrm and baf155 can interact specifically with msin3a in vitro showing a direct association of hswisnf complexes with proteins involved in gene repression these unexpected functional characteristics indicate that these hswisnf complexes play diverse regulatory roles