for these subunits in specific targeting to regions of the genome. However, this explanation now seems unlikely because mutations in the subunits involved had phenotypes nearly identical to rapid conditional deletion of the Brg and/or Brm ATPase (32–35), indicating that individual subunit function was central to the fundamental mechanism of the complexes. In addition, these essential subunits are dedicated to the BAF complex, as indicated by the fact that they comigrate with the 2-MDa complex and can be completely depleted using high-affinity antibodies to the other subunits (19, 36). These doubts about the fundamental mechanism of chromatin remodelers were further reinforced when several unexpectedly instructive functions of these complexes were discovered in the conversion of fibroblasts to induced pluripotent stem cells (37) and the conversion of human fibroblasts to neurons (31, 38). Indeed, a large number of highly instructive functions have been described in flies and worms, including instructive functions in the targeting of dendritic trees to their proper termini (39) and cell type specification (40–42). More recently, the model in which a transcription factor recruits complexes has been questioned by genomic studies in ES cells (11). Also, the ability of oncogenic BAF complexes to activate genes in heterochromatin where
