BAZ1B is an atypical tyrosine-protein kinase and regulatory subunit of ATP-dependent ISWI chr7 remodeling complexes (WICH-1 and WICH-5) that orchestrates multiple nuclear processes 1. As a chr7 remodeler, BAZ1B regulates nucleosome spacing and positioning to facilitate DNA replication, transcription, and repair 23. BAZ1B phosphorylates histone H2AX at tyrosine-142, generating H2AXY142ph, which distinguishes apoptotic from repair responses to DNA damage 14. The protein regulates transcription across all three RNA polymerases and mediates recruitment of WICH-5 complexes to replication forks 56. Beyond chr7 remodeling, BAZ1B modulates PCNA de-ubiquitination during DNA repair by directly interacting with ATAD5, preventing premature restoration of high-fidelity synthesis after lesion bypass 7. BAZ1B haploinsufficiency contributes to Williams syndrome (7q11.23 microdeletion), affecting craniofacial development through neural crest regulation and cognitive/behavioral phenotypes 89. Recent evidence links BAZ1B variants to gout susceptibility via serum uric acid metabolism 10. BAZ1B functions as a versatile 'protean protein' integrating chr7 architecture, transcriptional control, and DNA damage responses 11.