title: Loss of WSTF results in spontaneous fluctuations of heterochromatin formation and resolution, combined with substantial changes to gene expression.
abstract: BACKGROUND
  Williams syndrome transcription factor (WSTF) is a multifaceted protein that is involved in several nuclear processes, including replication, transcription, and the DNA damage response. WSTF participates in a chromatin-remodeling complex with the ISWI ATPase, SNF2H, and is thought to contribute to the maintenance of heterochromatin, including at the human inactive X chromosome (Xi). WSTF is encoded by BAZ1B, and is one of twenty-eight genes that are hemizygously deleted in the genetic disorder Williams-Beuren syndrome (WBS).
  
  
  RESULTS
  To explore the function of WSTF, we performed zinc finger nuclease-assisted targeting of the BAZ1B gene and isolated several independent knockout clones in human cells. Our results show that, while heterochromatin at the Xi is unaltered, new inappropriate areas of heterochromatin spontaneously form and resolve throughout the nucleus, appearing as large DAPI-dense staining blocks, defined by histone H3 lysine-9 trimethylation and association of the proteins heterochromatin protein 1 and structural maintenance of chromosomes flexible hinge domain containing 1. In three independent mutants, the expression of a large number of genes were impacted, both up and down, by WSTF loss.
  
  
  CONCLUSIONS
  Given the inappropriate appearance of regions of heterochromatin in BAZ1B knockout cells, it is evident that WSTF performs a critical role in maintaining chromatin and transcriptional states, a property that is likely compromised by WSTF haploinsufficiency in WBS patients.
authors.forename: Ashley E
authors.initials: AE
authors.lastname: Culver-Cochran
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee, FL, USA. chadwick@bio.fsu.edu.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Chadwick
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D042002:Chromatin Assembly and Disassembly; D041321:Chromosomes, Human, X; D055786:Gene Knockout Techniques; D057895:Haploinsufficiency / Q000235:genetics; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D018980:Williams Syndrome / Q000235:genetics*; D000092468:Bromodomain Containing Proteins
chemical_list: D006570:Heterochromatin; D006657:Histones; D014157:Transcription Factors; C116750:BAZ1B protein, human; D000092468:Bromodomain Containing Proteins