BAZ1B (also known as Williams-Beuren syndrome transcription factor, WSTF) is a component of the WICH complex (WSTF-ISWI ATP-dependent chromatin-remodelling complex). It has intrinsic tyrosine kinase activity by means of a domain that shares no sequence homology to any known kinase fold. It has been shown to phosphorylate Tyr 142 of H2A []. It is involved in chromatin assembly, RNA polymerase I and III gene regulation, vitamin D metabolism, and DNA repair [].