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Human telomeric protein TRF2 associates with genomic double-strand breaks as an early response to DNA damage

Paul S Bradshaw1, Dimitrios J Stavropoulos, M Stephen Meyn

  • 1Program in Genetics and Genomic Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.

Nature Genetics
|January 25, 2005
PubMed

Insights

The protein TRF2 rapidly binds to DNA double-strand breaks (DSBs) before the ATM pathway is activated. This suggests TRF2 plays a crucial role in the initial recognition of DNA damage.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genetics

Background:

  • Cellular DNA damage surveillance networks detect double-strand breaks (DSBs) to initiate repair, cell cycle arrest, or apoptosis.
  • Telomeres are protected from DSB recognition by the protein TRF2, which organizes them into T loops.
  • The precise role of TRF2 in non-telomeric DNA damage response remains unclear.

Purpose of the Study:

  • To investigate the role of TRF2 in the immediate response to photo-induced DNA double-strand breaks (DSBs) in human cells.
  • To determine the molecular requirements for TRF2 association with DSBs.
  • To elucidate the temporal relationship between TRF2 recruitment and the activation of canonical DSB response pathways.

Main Methods:

  • Irradiation of human fibroblasts to induce photo-DSBs.
  • Immunofluorescence microscopy to visualize TRF2 and gammaH2AX foci.
  • Analysis of TRF2 DSB association in cells with depleted or non-functional key DNA repair proteins (ATM, DNA-PK, MRN, Ku70, WRN, BLM).
  • Assessment of ATM signaling pathway activation via phosphorylation of its targets.

Main Results:

  • TRF2 rapidly associates with non-telomeric DSBs within 2 seconds of irradiation in human fibroblasts.
  • TRF2 forms transient foci that closely colocalize with DSBs, distinct from the gammaH2AX marker.
  • TRF2 recruitment to DSBs depends on its basic domain but not its Myb domain.
  • TRF2's association with DSBs occurs independently of ATM, DNA-PK, MRN complex, Ku70, WRN, and BLM.
  • Overexpression of TRF2 inhibits ATM signaling activation in response to DSBs.

Conclusions:

  • TRF2 is involved in the initial recognition and processing of DNA double-strand breaks (DSBs).
  • TRF2 acts upstream of the ATM-dependent DNA damage response network.
  • These findings reveal a novel, early role for TRF2 in sensing non-telomeric DNA damage.

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