Alternative subunits of the PBAF-nucleosome complex are indicated. cBAF is typically found at enhancers and grabs a nucleosome like a C-clamp, where SMARCA4 (green) and SMARCB1 (light blue) bind to histone surfaces exposed on the faces of the nucleosome (black dotted lines) and the ATPase domain of SMARCA4 engages with nucleosomal DNA and generates torque near SHL 2 (red dotted circle). Without SMARCB1-histone contacts, most of the core module may be free to flex and interact with nearby DNA or non-nucleosomal targets. The PBAF complex, which is typically found at active promoters, shares many core components with cBAF with the indicated alternative subunits, and binds nucleosomes similarly.
