Atypical tyrosine-protein kinase that plays a central role in chromatin remodeling and acts as a transcription regulator (PubMed:19092802). Involved in DNA damage response by phosphorylating 'Tyr-142' of histone H2AX (H2AXY142ph) (PubMed:19092802, PubMed:19234442). H2AXY142ph plays a central role in DNA repair and acts as a mark that distinguishes between apoptotic and repair responses to genotoxic stress (PubMed:19092802, PubMed:19234442). Regulatory subunit of the ATP-dependent WICH-1 and WICH-5 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:11980720, PubMed:28801535). Both 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 WICH-1 ISWI chromatin remodeling complex has a lower ATP hydrolysis rate than the WICH-5 ISWI chromatin remodeling complex (PubMed:28801535). The WICH-5 ISWI chromatin-remodeling complex regulates the transcription of various genes, has a role in RNA polymerase I transcription (By similarity). Within the B-WICH complex has a role in RNA polymerase III transcription (PubMed:16603771). Mediates the recruitment of the WICH-5 ISWI chromatin remodeling complex to replication foci during DNA replication (PubMed:15543136). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Component of the WICH-1 ISWI chromatin remodeling complex, at least composed of SMARCA1 and BAZ1B/WSTF, which regulates the spacing of histone octamers on the DNA template to facilitate access to DNA (PubMed:28801535). Within the WICH-1 ISWI chromatin remodeling complex interacts with SMARCA1; the interaction is direct (PubMed:28801535). Component of the WICH-5 ISWI chromatin remodeling complex (also called the WICH complex), at least composed of SMARCA5/SNF2H and BAZ1B/WSTF, which regulates the spacing of histone octamers on the DNA template to facilitate access to DNA (PubMed:11980720, PubMed:28801535). Within the WICH-5 ISWI chromatin remodeling complex interacts with SMARCA5/SNF2H; the interaction is direct (PubMed:11980720, PubMed:15543136, PubMed:28801535). Component of the B-WICH chromatin remodeling complex, at least composed of SMARCA5/SNF2H, BAZ1B/WSTF, SF3B1, DEK, MYO1C, ERCC6, MYBBP1A and DDX21 (PubMed:16603771). Within the B-WICH chromatin remodeling complex, interacts with SMARCA5/SNF2H, DDX21, DEK, MYBBP1A, SF3B1, ERCC6 and MYO1C (PubMed:16603771). Interacts with PCNA; the interaction is direct and is required for BAZ1B/WSTF binding to replication foci during S phase (PubMed:15543136). Interacts with CDT1 (PubMed:18162579). Accumulates in pericentromeric heterochromatin during replication. Co-localizes with PCNA at replication foci during S phase (PubMed:15543136). Co-localizes with SMARCA5/SNF2H at replication foci during late-S phase (PubMed:15543136). Also localizes to replication foci independently of SMARCA5/SNF2H and PCNA (PubMed:15543136). Ubiquitously expressed with high levels of expression in heart, brain, placenta, skeletal muscle and ovary. Expressed at equal levels in 19-23 weeks old fetal tissues. BAZ1B is located in the Williams-Beuren syndrome (WBS) critical region. WBS results from a hemizygous deletion of several genes on chromosome 7q11.23, thought to arise as a consequence of unequal crossing over between highly homologous low-copy repeat sequences flanking the deleted region. Haploinsufficiency of BAZ1B may be the cause of certain cardiovascular and musculo-skeletal abnormalities observed in the disease. Belongs to the WAL family. BAZ1B subfamily. Was shown to interact with VDR and with acetylated histones via its Bromo domain, but this work has later been retracted. Contaminating sequence. Potential poly-A sequence.