Atypical tyrosine-protein kinase that plays a central role in chromatin remodeling and acts as a transcription regulator (By similarity). Involved in DNA damage response by phosphorylating 'Tyr-142' of histone H2AX (H2AXY142ph) (PubMed:19092802). 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). 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). 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:16514417). The WICH-1 ISWI chromatin remodeling complex has a lower ATP hydrolysis rate than the WICH-5 ISWI chromatin remodeling complex (By similarity). The WICH-5 ISWI chromatin remodeling complex regulates the transcription of various genes, has a role in RNA polymerase I transcription (PubMed:16514417). Within the B-WICH complex has a role in RNA polymerase III transcription (By similarity). Mediates the recruitment of the WICH-5 ISWI chromatin remodeling complex to replication foci during DNA replication (By similarity). 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 (By similarity). Within the WICH-1 ISWI chromatin remodeling complex interacts with SMARCA1; the interaction is direct (By similarity). 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:16514417). Within the WICH-5 ISWI chromatin remodeling complex interacts with SMARCA5/SNF2H; the interaction is direct (PubMed:16514417, PubMed:19092802). Component of the B-WICH chromatin remodeling complex, at least composed of SMARCA5/SNF2H, BAZ1B/WSTF, SF3B1, DEK, MYO1C, ERCC6, MYBBP1A and DDX21 (By similarity). Within the B-WICH chromatin remodeling complex, interacts with SMARCA5/SNF2H, DDX21, DEK, MYBBP1A, SF3B1 and ERCC6 (By similarity). Interacts with MYO1C (PubMed:16514417). Interacts with PCNA; the interaction is direct and is required for BAZ1B/WSTF binding to replication foci during S phase (By similarity). Interacts with CDT1 (By similarity). Accumulates in pericentromeric heterochromatin during replication. Targeted to replication foci throughout S phase via its association with PCNA (By similarity). Expressed as early as day 7 and in equal amounts during gestation. Belongs to the WAL family. BAZ1B subfamily.