DNA聚合酶β对DNAγ线辐射损伤的修复作用

Roles of DNA polymerase β on repair of DNA damaged by γ-rays irradiation

采用ＤＮＡ聚合酶专一性抑制剂，观察ＤＮＡ聚合酶β对ＤＮＡγ线损伤的修复作用。结果表明：在重组大鼠ＤＮＡ聚合酶β作用下，［３￣Ｈ］－ＴＴＰ掺入率明显高于未照组（Ｐ＜０．０１）；在一定剂量范围内（肝细胞小于２０Ｇｙ，ＳＭＭＣ－ＬＴＮＭ肝癌细胞小于５Ｇｙ），［￣３Ｈ］－ＴＴＰ掺入率随照射剂量增加而升高，继续增加照射剂量时，［￣３Ｈ］－ＴＴＰ掺入率反而下降；在同一剂量下，不同剂量率照射组之间ＤＮＡ聚合酶β的修复合成无显著差别（Ｐ＞０．０５）。提示ＤＮＡ聚合酶β参与了γ线所致ＤＮＡ损伤的修复过程，并且这一修复作用同受照剂量以及细胞类型可能有关。

The roles of DNA polymerase β in the repair synthesis of γ-rays irradiated DNA from calf thymus, SMMC-LTNM hepatoma and nude mouse hepatocytes were evaluated, using NEM or d2 TTP as selective inhibitors to DNA polymerase α or β.It was observed that the rate of[3H]-TTP incorporating into calf thymus DNA damaged by 10 Gy γ-rays exposure was much higher(P<0.01) than that of the non-irradiated one,when there was some amount of recombinant rat DNA polymerase β in the reaction mixture.We also found that the [3H]-TTP incorporation rate reflecting the DNA repair synthesis increased gradually as the γ-rays absorbed dose rose to 20 Gy for hepatocyte nuclei or to 5 Gy for hepatoma nuclei, and then decreased slowly as the absorbed dose rose higher. These results suggest that DNA polymerase β could participate in DNA repair synthesis in both normal and neoplastic nuclei irradiated by γ-rays and its roles in DNA repair may be related to cell types and absorbed dose.