A SWI/SNF-specific Ig-like domain, SWIFT, is a transcription factor binding platform

Mammalian switch/sucrose nonfermenting (mSWI/SNF) chromatin remodeling complexes modulate DNA accessibility and gene expression; however, their genomic targeting mechanisms remain incompletely understood. Here, we identify SWIFT [SWI/SNF immunoglobulin fold (Ig-fold) for transcription factor interactions], a conserved transcription factor (TF) binding domain on the SMARCD subunits. SWIFT is necessary and sufficient for direct engagement with the transactivation domain of the PU.1 TF. A single amino acid mutation disrupts PU.1-mSWI/SNF binding, impairs complex targeting, and attenuates oncogenic transcription and proliferation in PU.1-dependent human cancer cells. Dominant expression of the SWIFT domain in isolation sequesters TFs from mSWI/SNF and poisons TF-"addicted" cancer cells. Finally, TFs across diverse families interact with SMARCD paralog-specific SWIFT domains. These results define a major mechanism of cell type- and disease-specific mSWI/SNF chromatin targeting and inform approaches toward therapeutic modulation.