Catalytically inactive when either DNA or nucleosomes are the substrate and does not possess chromatin-remodeling activity (PubMed:15310751, PubMed:28801535). Acts as a negative regulator of chromatin remodelers by generating inactive complexes (PubMed:15310751). Helicase that possesses intrinsic ATP-dependent chromatin-remodeling activity (PubMed:15310751, PubMed:14609955, PubMed:15640247, PubMed:28801535). ATPase activity is substrate-dependent, and is increased when nucleosomes are the substrate, but is also catalytically active when DNA alone is the substrate (PubMed:15310751, PubMed:14609955, PubMed:15640247). Catalytic subunit of ISWI chromatin-remodeling complexes, which form ordered nucleosome arrays on chromatin and facilitate access to DNA during DNA-templated processes such as DNA replication, transcription, and repair (PubMed:15310751, PubMed:14609955, PubMed:15640247, PubMed:28801535). Within the ISWI chromatin-remodeling complexes, slides edge- and center-positioned histone octamers away from their original location on the DNA template (PubMed:28801535). Catalytic activity and histone octamer sliding propensity is regulated and determined by components of the ISWI chromatin-remodeling complexes (PubMed:28801535). The BAZ1A-, BAZ1B-, BAZ2A- and BAZ2B-containing ISWI chromatin-remodeling complexes regulate the spacing of nucleosomes along the chromatin and have the ability to slide mononucleosomes to the center of a DNA template (PubMed:28801535). The CECR2- and RSF1-containing ISWI chromatin-remodeling complexes do not have the ability to slide mononucleosomes to the center of a DNA template (PubMed:28801535). Within the NURF-1 and CERF-1 ISWI chromatin remodeling complexes, nucleosomes are the preferred substrate for its ATPase activity (PubMed:14609955, PubMed:15640247). Within the NURF-1 ISWI chromatin-remodeling complex, binds to the promoters of En1 and En2 to positively regulate their expression and promote brain development (PubMed:14609955). May promote neurite outgrowth (PubMed:14609955). May be involved in the development of luteal cells (PubMed:16740656). May form homodimers (PubMed:15310751). Component of the BPFT-SMARCA1 complex at least composed of SMARCA1, BPFT, RBBP4 and RBBP7; the complex is catalytically inactive and does not remodel chromatin (PubMed:15310751). Within the complex interacts with BPTF, RBBP4 and RBBP7 (PubMed:15310751). Component of the BAZ1A-1-SMARCA1 complex at least composed of SMARCA1 and BAZ1A; the complex is catalytically inactive and does not remodel chromatin (PubMed:28801535). Component of the BAZ1B-1-SMARCA1 complex at least composed of SMARCA1 and BAZ1B; the complex is catalytically inactive and does not remodel chromatin (PubMed:28801535). May form homodimers (PubMed:15310751). Component of the ACF-1 ISWI chromatin remodeling complex at least composed of SMARCA1 and BAZ1A, which regulates the spacing of histone octamers on the DNA template to facilitate access to DNA (PubMed:28801535). Within the complex interacts with BAZ1A; the interaction is direct (PubMed:28801535). Component of the WICH-1 ISWI chromatin remodeling complex at least composed of SMARCA1 and BAZ1B/WSTF (PubMed:28801535). Within the complex interacts with BAZ1B/WSTF (PubMed:28801535). Component of the NoRC-1 ISWI chromatin remodeling complex at least composed of SMARCA1 and BAZ2A/TIP5 (PubMed:28801535). Within the complex interacts with BAZ2A/TIP5 (PubMed:28801535). Component of the BRF-1 ISWI chromatin remodeling complex at least composed of SMARCA1 and BAZ2B (PubMed:28801535). Within the complex interacts with BAZ2B (PubMed:28801535). Component of the NURF-1 ISWI chromatin remodeling complex (also called the nucleosome-remodeling factor (NURF) complex) at least composed of SMARCA1, BPTF, RBBP4 and RBBP7 (PubMed:14609955, PubMed:15640247, PubMed:28801535). Within the complex interacts with BPTF (PubMed:15310751, PubMed:14609955, PubMed:28801535). Within the complex interacts with RBBP4 and RBBP7 (PubMed:15310751, PubMed:14609955). Component of the CERF-1 ISWI chromatin remodeling complex (also called the CECR2-containing-remodeling factor (CERF) complex) at least composed of CECR2 and SMARCA1 (PubMed:15640247, PubMed:28801535). Within the complex interacts with CECR2 (PubMed:28801535). Component of the RSF-1 ISWI chromatin remodeling complex at least composed of SMARCA1 and RSF1 (PubMed:15640247, PubMed:28801535). Within the complex interacts with RSF1 (PubMed:28801535). Interacts with PRLR (PubMed:16740656). Interacts with ERCC6 (PubMed:26030138). Mainly expressed in non-neuronal tissues such as lung, breast, kidney, and ovary. Expressed in lung, breast, kidney, ovary, skeletal muscle and brain. Inactive as an ATPase due to the presence of exon 13, but retains its ability to correctly fold and incorporate into complexes. Active as an ATPase due to the absence of exon 13. Belongs to the SNF2/RAD54 helicase family. ISWI subfamily.