Chromatin relaxation in response to DNA double-strand breaks is modulated by a novel ATM- and KAP-1 dependent pathway

Nat Cell Biol. 2006 Aug;8(8):870-6. doi: 10.1038/ncb1446. Epub 2006 Jul 23.


The cellular DNA-damage response is a signaling network that is vigorously activated by cytotoxic DNA lesions, such as double-strand breaks (DSBs). The DSB response is mobilized by the nuclear protein kinase ATM, which modulates this process by phosphorylating key players in these pathways. A long-standing question in this field is whether DSB formation affects chromatin condensation. Here, we show that DSB formation is followed by ATM-dependent chromatin relaxation. ATM's effector in this pathway is the protein KRAB-associated protein (KAP-1, also known as TIF1beta, KRIP-1 or TRIM28), previously known as a corepressor of gene transcription. In response to DSB induction, KAP-1 is phosphorylated in an ATM-dependent manner on Ser 824. KAP-1 is phosphorylated exclusively at the damage sites, from which phosphorylated KAP-1 spreads rapidly throughout the chromatin. Ablation of the phosphorylation site of KAP-1 leads to loss of DSB-induced chromatin decondensation and renders the cells hypersensitive to DSB-inducing agents. Knocking down KAP-1, or mimicking a constitutive phosphorylation of this protein, leads to constitutive chromatin relaxation. These results suggest that chromatin relaxation is a fundamental pathway in the DNA-damage response and identify its primary mediators.

Publication types

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

MeSH terms

  • Ataxia Telangiectasia Mutated Proteins
  • Blotting, Western
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology*
  • Cell Line
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Chromatin / metabolism*
  • DNA Damage*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / physiology*
  • Dose-Response Relationship, Drug
  • Humans
  • Microscopy, Fluorescence
  • Mutation / genetics
  • Nucleic Acid Synthesis Inhibitors / pharmacology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism
  • Protein-Serine-Threonine Kinases / physiology*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Repressor Proteins / physiology*
  • Signal Transduction / physiology*
  • Tripartite Motif-Containing Protein 28
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism
  • Tumor Suppressor Proteins / physiology*
  • Zinostatin / pharmacology


  • Cell Cycle Proteins
  • Chromatin
  • DNA-Binding Proteins
  • Nucleic Acid Synthesis Inhibitors
  • Repressor Proteins
  • Tumor Suppressor Proteins
  • Zinostatin
  • TRIM28 protein, human
  • Tripartite Motif-Containing Protein 28
  • ATM protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Protein-Serine-Threonine Kinases