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Poly(ADP-ribose) polymerase 1 is inhibited by a histone H2A variant, MacroH2A, and contributes to silencing of the inactive X chromosome.

Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear enzyme that is involved in modulating chromatin structure, regulation of gene expression, and sensing DNA damage. Here, we report that PARP-1 enzymatic activity is inhibited by macroH2A, a vertebrate histone H2A variant that is enriched on facultative heterochromatin. MacroH2A family members have a large C-terminal non-histone domain (NHD) and H2A-like histone domain. MacroH2A1.2 and PARP-1 interact in vivo and in vitro via the NHD. The NHD of each macroH2A family member was sufficient to inhibit PARP-1 enzymatic activity in vitro. The NHD of macroH2A1.2 was a mixed inhibitor of PARP-1 catalytic activity, with affects on both catalytic activity and the substrate binding affinity of PARP-1. Depletion of PARP-1 by RNA interference caused reactivation of a reporter gene on the inactive X chromosome, demonstrating that PARP-1 participates in the maintenance of silencing. These results suggest that one function of macroH2A in gene silencing is to inhibit PARP-1 enzymatic activity, and this may affect PARP-1 association with chromatin.

Pubmed ID: 17322296


  • Nusinow DA
  • Hernández-Muñoz I
  • Fazzio TG
  • Shah GM
  • Kraus WL
  • Panning B


The Journal of biological chemistry

Publication Data

April 27, 2007

Associated Grants

  • Agency: NIDDK NIH HHS, Id: R01 DK069710
  • Agency: NIDDK NIH HHS, Id: R01 DK069710
  • Agency: NIGMS NIH HHS, Id: R01 GM63671

Mesh Terms

  • Cell Line
  • Chromatin
  • Chromatin Assembly and Disassembly
  • Gene Silencing
  • Histones
  • Poly(ADP-ribose) Polymerases
  • Protein Binding
  • Protein Structure, Tertiary
  • X Chromosome Inactivation