resulting in arrested thymocyte development47. This mode of action is distinct from that of the yeast Swi/Snf complex, which in all cases investigated is recruited to promoters by transcription factors in order to activate transcription48. Surprisingly, in mice, BRG1 is required again at a later stage to activate CD4 expression, indicating that BAF complexes can both activate and repress the transcription of a single gene10 depending on the developmental context. Because mammalian BAF complexes often repress transcription at a distance, whereas the yeast Swi/Snf complex always activates transcription by binding to promoters, there are likely to be significant mechanistic differences between these two complexes. These observations indicate that the initial nomenclature that we proposed, mSWI/SNF49, may be an inappropriate extrapolation.
