SWI/SNF complexes facilitate gene activation and transcription factor binding byaltering repressive chromatin structures. In mammals, SWI/SNF complexes are present inmutliple forms that include 9-12 proteins called BRG1-associated factors (BAFs), whichrange in molecular weight from 47 to 250 kDa. BAF60 is the homologue of the yeastSWP70 subunit of the yeast SWI/SNF complex that regulates glucocorticoidtranscription. Three isoforms of BAF60 are BAF60a, BAF60b, and BAF60c. BAF60a isubiquitously expressed and is present in the 200-kDa BRG1 complex. BAF60b andBAF60c are expressed preferentially in muscle and pancreas and may be subunits of adistinct complex that shares some subunits with BRG1 complex. In hematopoietic cells,a SWI/SNF related-complex (PYR) contains BAF57, INI1, BAF60a, and BAF170. This complex binds a 250 bp pyrimidine-rich element between the fetal and adult ß-globingenes and may facilitate human fetal-to-adult globin gene switching. Thus, BAF60proteins are components of multiple SWI/SNF complexes that regulate the transcriptionof various genes.