review). Hence, it is becoming clear that SWI-like remodellers are intricately involved in many aspects of cell biology beyond transcription. Second, even within their traditional role of transcriptional regulation, ATP-dependent chromatin remodellers do not function in a consistent manner. Brahma-associated factor (BAF) complexes, which belong to the SWI/SNF family, can function as both transcriptional activators and repressors and can even switch between these two modes of action at the same gene10. In addition, tissue-specific BAF complexes have been reported to interact with a variety of transcription factors in different cell types (see ref. 11 for a review), allowing the complexes to take on context-dependent functions arising from their different interaction partners. For these reasons, the roles of ATP-dependent chromatin remodelling may be wider, yet more precise and programmatic, than was previously thought. Indeed, modulating the expression of a single target gene can partly suppress the phenotypes of mutations in the BAF complex in the heart12 and in post-mitotic neurons13. This focus on a single target is also seen for polycomb group (PcG) proteins. These proteins mediate transcriptional repression and often oppose the function of trithorax group (TrxG) genes such as those encoding BRG1 and MLL (discussed in the next section),
