Identification of assembly mode of non-canonical BAF (ncBAF) chromatin remodeling complex core module

Mammalian SWI/SNF (mSWI/SNF) ATP-dependent chromatin remodeling complexes play critical roles in regulating gene expression and DNA accessibility, and more than 20 % of cancers have mutations in genes encoding chromatin remodeling complexes. The mSWI/SNF family comprises three distinct classes: canonical BAF (cBAF), PBAF, and non-canonical BAF (ncBAF). While the structures of cBAF and PBAF have been resolved by using cryo-electron microscopy (cryo-EM), the modular organization and assembly mechanism of ncBAF remain poorly understood. In this study, we first mapped the binding fragment of SMARCC1/SMARCD1 complex, then found that GLTSCR1(1041-1204) could form a stable complex with SMARCC1(447-966)/SMARCD1(129-515). Next, we purified the SMARCC1(447-966)/SMARCD1(117-515)/GLTSCR1(1041-1204)/BRD9(266-510) tetrameric complex. Finally, we assembled a stable and uniform SMARCC1(447-966)/SMARCD1(117-515)/GLTSCR1(1041-1204)/BRD9(266510)/SMARCA4(289-464) quinary complex in vitro, which is ncBAF core module. These findings provide insight into the assembly mode of ncBAF complex, and lay the foundations for further solving its structure in the future.