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ATM phosphorylation of Nijmegen breakage syndrome protein is required in a DNA damage response

X Wu1, V Ranganathan, D S Weisman

  • 1Dana Farber Cancer Institute, Boston, Massachusetts 02115, USA.

Nature
|June 6, 2000
PubMed

Insights

Nijmegen breakage syndrome (NBS) protein phosphorylation by ATM kinase is crucial for DNA damage response. This ATM-mediated phosphorylation of NBS is essential for human cell survival following gamma-radiation exposure.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cell Biology

Background:

  • Nijmegen breakage syndrome (NBS) presents with extreme radiation sensitivity, chromosomal instability, and cancer.
  • NBS shares phenotypes with ataxia telangiectasia mutated (ATM) disease, suggesting common DNA damage response pathways.
  • ATM is a protein kinase activated by DNA damage.

Purpose of the Study:

  • To investigate the role of NBS protein phosphorylation in response to DNA damage.
  • To determine if ATM kinase phosphorylates NBS protein.
  • To elucidate the functional significance of ATM-dependent NBS phosphorylation in cellular responses to radiation.

Main Methods:

  • Investigated NBS protein phosphorylation upon exposure to gamma-radiation, UV light, and hydroxyurea.
  • Compared NBS phosphorylation levels in normal and ATM-deficient cells.
  • Utilized in vitro kinase assays to identify ATM-phosphorylated serine residues on NBS.
  • Generated NBS mutants with inactivated ATM-dependent phosphorylation sites.
  • Assessed the impact of NBS phosphorylation status on clonogenic survival after gamma-radiation.

Main Results:

  • NBS protein is specifically phosphorylated in response to gamma-radiation, UV light, and hydroxyurea.
  • Gamma-radiation-induced NBS phosphorylation is significantly reduced in ATM-deficient cells.
  • ATM kinase directly phosphorylates NBS protein at specific serine residues (S343, S397, S615) in vitro.
  • Mutating these ATM-dependent sites impairs NBS phosphorylation and reduces cell survival after gamma-radiation.

Conclusions:

  • ATM-dependent phosphorylation of NBS is critical for the cellular response to DNA damage, particularly gamma-radiation.
  • This phosphorylation event is essential for maintaining genomic stability and cell survival in response to genotoxic stress.
  • Findings highlight a key regulatory mechanism in DNA repair pathways involving NBS and ATM.

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