DNA processing is not required for ATM-mediated telomere damage response after TRF2 deletion

Nat Cell Biol. 2005 Jul;7(7):712-8. doi: 10.1038/ncb1275. Epub 2005 Jun 19.


Telomere attrition and other forms of telomere damage can activate the ATM kinase pathway. What generates the DNA damage signal at mammalian chromosome ends or at other double-strand breaks is not known. Telomere dysfunction is often accompanied by disappearance of the 3' telomeric overhang, raising the possibility that DNA degradation could generate the structure that signals. Here we address these issues by studying telomere structure after conditional deletion of mouse TRF2, the protective factor at telomeres. Upon removal of TRF2 from TRF2(F/-) p53-/- mouse embryo fibroblasts, a telomere damage response is observed at most chromosome ends. As expected, the telomeres lose the 3' overhang and are processed by the non-homologous end-joining pathway. Non-homologous end joining of telomeres was abrogated in DNA ligase IV-deficient (Lig4-/-) cells. Unexpectedly, the telomeres of TRF2-/- Lig4-/- p53-/- cells persisted in a free state without undergoing detectable DNA degradation. Notably, the telomeres retained their 3' overhangs, but they were recognized as sites of DNA damage, accumulating the DNA damage response factors 53BP1 and gamma-H2AX, and activating the ATM kinase. Thus, activation of the ATM kinase pathway at chromosome ends does not require overhang degradation or other overt DNA processing.

Publication types

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

MeSH terms

  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / metabolism*
  • Cells, Cultured
  • Checkpoint Kinase 2
  • Chromosomal Proteins, Non-Histone
  • Crosses, Genetic
  • DNA / genetics
  • DNA / metabolism*
  • DNA Damage*
  • DNA Ligase ATP
  • DNA Ligases / genetics
  • DNA-Binding Proteins / metabolism*
  • Embryo, Mammalian / cytology
  • Fibroblasts / cytology
  • Fibroblasts / metabolism
  • Gene Deletion
  • Histones / metabolism
  • In Situ Hybridization, Fluorescence
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Protein Serine-Threonine Kinases / metabolism*
  • Telomere / genetics
  • Telomere / metabolism*
  • Telomeric Repeat Binding Protein 1 / metabolism
  • Telomeric Repeat Binding Protein 2 / genetics*
  • Telomeric Repeat Binding Protein 2 / metabolism
  • Transfection
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Proteins / metabolism*
  • Tumor Suppressor p53-Binding Protein 1
  • rap1 GTP-Binding Proteins / metabolism


  • Cell Cycle Proteins
  • Chromosomal Proteins, Non-Histone
  • DNA-Binding Proteins
  • Histones
  • Intracellular Signaling Peptides and Proteins
  • Phosphoproteins
  • Telomeric Repeat Binding Protein 1
  • Telomeric Repeat Binding Protein 2
  • Trp53bp1 protein, mouse
  • Tumor Suppressor Protein p53
  • Tumor Suppressor Proteins
  • Tumor Suppressor p53-Binding Protein 1
  • gamma-H2AX protein, mouse
  • DNA
  • Checkpoint Kinase 2
  • Ataxia Telangiectasia Mutated Proteins
  • Atm protein, mouse
  • Chek2 protein, mouse
  • Protein Serine-Threonine Kinases
  • rap1 GTP-Binding Proteins
  • DNA Ligases
  • DNA Ligase ATP