Comparison of the kinetics of radiation-induced apoptosis in DT40 cells irradiated with low and high doses of X rays.
In this study, we attempted to clarify the influence of the DNA repair genes RAD54 and KU70, components of the homologous recombination (HR) and non-homologous end-joining (NHEJ) pathways, respectively, on apoptosis induced by 1 Gy (low-dose) and 5 Gy (high-dose) irradiation. All experiments were performed using chicken B-lymphocyte DT40 cells and the DNA repair-deficient cell lines KU70(-/-), RAD54(-/-) and KU70(-/-)/RAD54(-/-). Morphological changes were detected by fluorescence methods, and the sub-G(1) fraction and the activated caspases in DT40 cells were analyzed by flow cytometry. Irradiation with 1 Gy significantly increased the level of apoptosis in cells with the defective DNA repair genes, with the maximum apoptosis occurring in double mutant cells, KU70(-/-)/RAD54(-/-), demonstrating that 1 Gy is enough to induce apoptosis in DNA repair-deficient DT40 cells, and that KU70 and RAD54 must have almost the same role in low-dose radiation-induced apoptosis. After 5 Gy, fast induction of apoptosis, within 2 h, was seen in both wild-type cells and RAD54(-/-) cells, indicating that functional KU70 must be important for the rescue of the cells from the induction of fast apoptosis.
Takahashi
Momoko
M
Heavy-ion Radiobiology Research Group, National Institute of Radiological Sciences, Anagawa, Chiba, 263-8555, Japan. takamomo@nirs.go.jp
Takakura
Kaoru
K
Furusawa
Yoshiya
Y
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D002645:Chickens; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation; D014965:X-Rays
D020169:Caspases