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DNA Damage and Cellular Stress Responses

Ataxia Telangiectasia-Mutated–Dependent DNA Damage Checkpoint Functions Regulate Gene Expression in Human Fibroblasts

¹ Department of Pathology and Laboratory Medicine, Center for Environmental Health and Susceptibility, and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and ² National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina

Requests for reprints: William K. Kaufmann, Department of Pathology and Laboratory Medicine and Lineberger Comprehensive Cancer Center, CB#7295, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295. Phone: 919-966-8209; Fax: 919-966-9673. E-mail: wkarlk{at}med.unc.edu

The relationships between profiles of global gene expression and DNA damage checkpoint functions were studied in cells from patients with ataxia telangiectasia (AT). Three telomerase-expressing AT fibroblast lines displayed the expected hypersensitivity to ionizing radiation (IR) and defects in DNA damage checkpoints. Profiles of global gene expression in AT cells were determined at 2, 6, and 24 h after treatment with 1.5-Gy IR or sham treatment and were compared with those previously recognized in normal human fibroblasts. Under basal conditions, 160 genes or expressed sequence tags were differentially expressed in AT and normal fibroblasts, and these were associated by gene ontology with insulin-like growth factor binding and regulation of cell growth. On DNA damage, 1,091 gene mRNAs were changed in at least two of the three AT cell lines. When compared with the 1,811 genes changed in normal human fibroblasts after the same treatment, 715 were found in both AT and normal fibroblasts, including most genes categorized by gene ontology into cell cycle, cell growth, and DNA damage response pathways. However, the IR-induced changes in these 715 genes in AT cells usually were delayed or attenuated in comparison with normal cells. The reduced change in DNA damage response genes and the attenuated repression of cell cycle–regulated genes may account for the defects in cell cycle checkpoint function in AT cells. (Mol Cancer Res 2007;5(8):813–22)