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Disruption of ATM in p53-null cells causes multiple functional abnormalities in cellular response to ionizing
1Department of Molecular Pathology, Faculty of Medicine, Kanazawa University, Ishikawa, Japan.
Abstract:
ATM is a member of the large phosphatidylinositol-3 kinase family and plays an important role in cellular response to DNA damage. To further define the physiological roles of ATM at the cellular level, we created an isogenic set of stable cell lines differing only in their ATM status from the chicken B cell line DT40 by targeted integration. These stable DT40 cell lines, as most of transformed chicken cell lines, do not express p53. However, ATM-/- DT40 cells displayed retarded cellular proliferation, defective G2/M checkpoint control and radio-resistant DNA synthesis. Furthermore, ATM-/- DT40 cells were sensitive to ionizing radiation and showed highly elevated frequencies of both spontaneous and radiation-induced chromosomal aberrations. In addition, a slight but significant reduction in targeted integration frequency was observed in ATM-/- DT40 cells. These results suggest that ATM has multiple p53-independent functions in cell cycle checkpoint control and in maintenance of chromosomal DNA. These ATM deficient DT40 clones therefore provide a useful model system for analysing p53-independent ATM functions.
Insights
The ATM protein is crucial for DNA damage response and cell cycle control, independent of p53. ATM-deficient cells show impaired proliferation, DNA repair, and chromosomal stability.
Area of Science:
- Cellular Biology
- Molecular Biology
- Genetics
Background:
- The ATM (ataxia-telangiectasia mutated) protein is a key kinase in the phosphatidylinositol-3 kinase family.
- ATM plays a critical role in cellular responses to DNA damage.
- Understanding ATM's functions, particularly p53-independent roles, is vital for cellular health.
Purpose of the Study:
- To investigate the physiological roles of ATM at the cellular level.
- To characterize p53-independent functions of ATM using a DT40 chicken B cell line model.
- To establish and utilize isogenic cell lines with varying ATM status.
Main Methods:
- Creation of isogenic DT40 cell lines with targeted integration to control ATM status (ATM-/-).
- Assessment of cellular proliferation rates.
- Analysis of cell cycle checkpoint control (G2/M).
- Evaluation of radio-resistant DNA synthesis.
- Measurement of sensitivity to ionizing radiation.
- Quantification of spontaneous and radiation-induced chromosomal aberrations.
- Determination of targeted integration frequency.
Main Results:
- ATM-/- DT40 cells exhibited retarded proliferation and defective G2/M checkpoint control.
- These cells displayed radio-resistant DNA synthesis and increased sensitivity to ionizing radiation.
- ATM deficiency led to significantly elevated frequencies of spontaneous and radiation-induced chromosomal aberrations.
- A slight but significant reduction in targeted integration frequency was noted in ATM-/- cells.
Conclusions:
- ATM possesses multiple p53-independent functions in cell cycle checkpoint control and chromosomal DNA maintenance.
- ATM-deficient DT40 cells serve as a valuable model for studying these p53-independent ATM functions.
- These findings highlight ATM's broad importance in genome stability and cellular response pathways.