Gene reactivation by 5-aza-2'-deoxycytidine-induced demethylation requires SRCAP-mediated H2A.Z insertion to establish nucleosome depleted regions

PLoS Genet. 2012;8(3):e1002604. doi: 10.1371/journal.pgen.1002604. Epub 2012 Mar 29.


5-Aza-2'-deoxycytidine, approved by the FDA for the treatment of myelodysplastic syndrome (MDS), is incorporated into the DNA of dividing cells where it specifically inhibits DNA methylation by forming covalent complexes with the DNA methyltransferases (DNMTs). In an effort to study the correlations between DNA methylation, nucleosome remodeling, and gene reactivation, we investigate the integrated epigenetic events that worked coordinately to reprogram the methylated and closed promoters back to permissive chromatin configurations after 5-Aza-2'-deoxycytidine treatment. The ChIP results indicate that H2A.Z is deposited at promoter regions by the Snf2-related CBP activator protein (SRCAP) complex following DNA demethylation. According to our genome-wide expression and DNA methylation profiles, we find that the complete re-activation of silenced genes requires the insertion of the histone variant H2A.Z, which facilitates the acquisition of regions fully depleted of nucleosome as demonstrated by NOMe-seq (Nucleosome Occupancy Methylome-sequencing) assay. In contrast, SRCAP-mediated H2A.Z deposition is not required for maintaining the active status of constitutively expressed genes. By combining Hpa II digestion with NOMe-seq assay, we show that hemimethylated DNA, which is generated following drug incorporation, remains occupied by nucleosomes. Our data highlight H2A.Z as a novel and essential factor involved in 5-Aza-2'-deoxycytidine-induced gene reactivation. Furthermore, we elucidate that chromatin remodeling translates the demethylation ability of DNMT inhibitors to their downstream efficacies, suggesting future therapeutic implications for chromatin remodelers.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases* / genetics
  • Adenosine Triphosphatases* / metabolism
  • Azacitidine / analogs & derivatives*
  • Azacitidine / pharmacology
  • Cell Line, Tumor
  • Chromatin Assembly and Disassembly / genetics*
  • DNA Methylation* / drug effects
  • DNA Methylation* / genetics
  • DNA Modification Methylases / antagonists & inhibitors
  • DNA Modification Methylases / metabolism
  • Decitabine
  • Epigenesis, Genetic
  • Gene Expression Regulation / drug effects
  • Gene Knockdown Techniques
  • Histones* / genetics
  • Histones* / metabolism
  • Humans
  • Nucleosomes* / genetics
  • Promoter Regions, Genetic
  • Transcriptional Activation / drug effects
  • Transcriptional Activation / genetics


  • Histones
  • Nucleosomes
  • histone H2A.F-Z
  • Decitabine
  • DNA Modification Methylases
  • Adenosine Triphosphatases
  • SRCAP protein, human
  • Azacitidine

Associated data

  • GEO/GSE26685