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Chk1 complements the G2/M checkpoint defect and radiosensitivity of ataxia-telangiectasia cells

P Chen1, M Gatei, M J O'Connell

  • 1The Queensland Institute of Medical Research, PO Royal Brisbane Hospital, Herston, Australia.

Oncogene
|February 2, 1999
PubMed

Insights

Overexpressing the Schizosaccaromyces pombe chk1 gene in ataxia-telangiectasia (A-T) cells restored the G2 checkpoint and improved survival after radiation exposure. This suggests chk1 acts downstream of ATM to correct the radiosensitive phenotype in A-T cells.

Area of Science:

  • Cell Biology
  • Genetics
  • Radiation Biology

Background:

  • Ataxia-telangiectasia (A-T) is a human genetic disorder characterized by defective cell cycle checkpoint activation following DNA damage.
  • The ATM protein kinase is crucial for DNA damage response and checkpoint control.
  • Understanding ATM's role in checkpoint regulation is key to addressing A-T cellular phenotypes.

Purpose of the Study:

  • To investigate if the fission yeast chk1 gene, a G2 DNA damage checkpoint regulator, could ameliorate the radiosensitive phenotype in A-T cells.
  • To determine the role of chk1 in relation to ATM in controlling cell cycle checkpoints and radiation sensitivity.

Main Methods:

  • Cloning of the fission yeast chk1 gene into an EBV-based vector with a metallothionein promoter.
  • Transfection of the chk1 construct into A-T lymphoblastoid cells.
  • Assessment of cell viability, chromosome aberrations, and cell cycle checkpoint function (G1/S and G2) following ionizing radiation exposure.

Main Results:

  • Induction of chk1 expression significantly enhanced A-T cell survival after radiation.
  • Chk1 expression led to a reduction in radiation-induced chromosome aberrations.
  • Restoration of the G2 DNA damage checkpoint was observed in A-T cells expressing chk1.
  • Chk1 expression did not correct the G1/S checkpoint or radioresistant DNA synthesis.

Conclusions:

  • Overexpressed chk1 acts downstream of ATM to restore the G2 checkpoint in A-T cells.
  • Chk1 expression can correct the radiosensitive phenotype associated with G2 checkpoint defects in A-T cells.
  • These findings help to dissociate specific checkpoint events and their contribution to the radiosensitive phenotype in A-T.

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