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Abstract

The sensors for the DNA response is divided into two main categories, DNA injury and DNA repair. This paper shows expressions γ-H2AX as the marker of DNA injury, and H-Ras dependant Ku80 expression for the DNA repair each. A role for γ-H2AX phosphrylation has been studied in DNA injury and repair, cell cycle checkpoints. In this paper, we examine the γ-H2AX and Ku80 expression on γ-ray or H2O2 treatment induced cytotoxicity using immunohistochemical and western blot methods. This paper shows that the expression of the Ras increased the Ku80 level, which is one of the key enzymes involved in repairing double-stranded DNA breaks(DSBs) at the sites of nucleus and cytoplasm. After exposing the cells to γ-irradiation or H2O2 treatment, γ-H2AX immnuoreactive nuclear granules were dramatically increased in the site of DSB in the parenchyme of nucleus. And it was also found that the expression of γ-H2AX was increased in after treating cytotoxic agent. Activated H-Ras expression in human fibroblast cell lines increases the activity of Ku80 to bind injuried DNA, reduces γ-H2AX expression by UV irradiation, and increases the activity of DSB repair. These results suggest that the increased γ-H2AX expression and the Ku80 expression may play important role in recognizing and protecting cells against celluar DNA damage.