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Single-stranded DNA induces ataxia telangiectasia mutant (ATM)/p53-dependent DNA damage and apoptotic signals

Alam Nur-E-Kamal1, Tsai-Kun Li, Ailing Zhang

  • 1Department of Pharmacology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA. nurekasa@umdnj.edu

The Journal of Biological Chemistry
|January 24, 2003
PubMed

Insights

Single-stranded DNA triggers DNA damage and apoptosis signals in mammalian cells. This suggests single-stranded DNA acts upstream of ATM/p53 in DNA damage response pathways.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Genetics

Background:

  • The initial trigger for DNA damage signaling pathways remains incompletely understood.
  • Single-stranded DNA (ssDNA) has been hypothesized as a potential initiator of these pathways.

Purpose of the Study:

  • To investigate the role of single-stranded DNA in initiating DNA damage and apoptosis signaling.
  • To elucidate the upstream signaling events involving ATM and p53.

Main Methods:

  • Introduction of diverse single-stranded DNA sequences into mammalian cells.
  • Assessment of DNA damage and apoptosis markers.
  • Analysis of p53 and ATM (ataxia telangiectasia mutant) activation via Western blotting and kinase assays.
  • Evaluation of apoptosis using caspase activity assays, cytochrome c release, and reactive oxygen species (ROS) production.
  • Functional assays in p53-deficient cells and using ATM small interfering RNA (siRNA).

Main Results:

  • Single-stranded DNA introduction induced significant DNA damage and apoptosis.
  • ssDNA exposure led to p53 upregulation and ATM activation, evidenced by histone H2AX phosphorylation.
  • Apoptosis markers, including caspase-dependent DNA breaks, cytochrome c release, and ROS production, were triggered by ssDNA.
  • Apoptosis induction by ssDNA was significantly attenuated in p53-null cells and cells with ATM knockdown.

Conclusions:

  • Single-stranded DNA acts as a potent inducer of DNA damage and apoptosis in mammalian cells.
  • These findings position single-stranded DNA upstream of the ATM/p53 pathway in the DNA damage response.
  • ssDNA represents a critical early signal in cellular response to DNA damage.

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