title: SWI/SNF-mediated chromatin remodeling induces Z-DNA formation on a nucleosome.
abstract: BACKGROUND
  Z-DNA is a higher-energy, left-handed form of the double helix. A primary function of Z-DNA formation is to facilitate transcriptional initiation and activation. Sequences favoring Z-DNA formation are frequently located in promoter regions and Z-DNA is stabilized by torsional strain resulting from negative supercoiling, such as that generated by an actively transcribing polymerase or by a nucleosome remodeling event. We previously have shown that activation of the CSF1 gene by a chromatin remodeling event in the promoter results in Z-DNA formation at TG repeats within the promoter.
  
  
  RESULTS
  We show that remodeling of a mononucleosome by the human SWI/SNF complex results in Z-DNA formation when the DNA within the mononucleosome contains Z-DNA favoring sequence. Nuclease accessibility patterns of nucleosome core particle consisting of Z-DNA are quite different from counterpart nucleosomes containing classic B-DNA. Z-nucleosomes represent a novel mononucleosome structure.
  
  
  CONCLUSIONS
  We present evidence that Z-DNA can form on nucleosomes though previous observations indicate the occlusion of nucleosome formation from Z-DNA.
authors.affiliation: Systems Biology Center, Division of Intramural Research, National Heart, Lung and Blood Institute, NIH, Maryland, USA. zhaok@nhlbi.nih.gov.
authors.forename: Niveen
authors.initials: N
authors.lastname: Mulholland
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugiyama
authors.forename: Keji
authors.initials: K
authors.lastname: Zhao