Rejoining Of DNA Double-strand Breaks In Ku80-deficient Mouse Fibroblasts

Objection: To confirm the importance of Ku protein in rejoining of DNA double stand breaks (DSBs) and study the relationship between the ability of DNA DSBs rejoining in Ku80-deficient mouse fibroblasts and various irradiation dose of x-ray.Method: Asymmetric Field Inversion Gel Electrophoresis (AFIGE) was used to evaluate the DNA damage in fibroblasts. These cells were derived from Ku80+/+, Ku80+/- and Ku80-/- mice and immortalized by transfection with plasmids containing the human MYC proto-oncogene. The cells were irradiated by x-ray at different doses and then allowed to repair for different time. The fractions of activity released (FAR) were compared between different cells and various irradiating doses to evaluate the radiosensitivity of DNA DSBs induced by x-ray and the ability of DNA DSB repair.Results: 1) The cells defective in Ku80 are extremely radiosensitive; 2) There are no significant differences in the yields of DNA DSB among the three cells lines; 3) Ku80 cells are severely deficient in the rejoining DNA DSB; 4) The deficiency is independent of the radiation dose used.Conclusion: Ku protein plays an important role in rejoining of DNA double stand breaks (DSBs) induced by x-ray. The deficiency of DSBs rejoining in Ku80-/- cell is independent.