人pol-β高表达对细胞应对DNA损伤反应时的影响

Effects of overexpression of human pol-β on cellular response to DNA damage

目的探讨DNA聚合酶beta（pol-β）高表达对细胞应对遗传损伤反应的影响。方法转染筛选人pol-β稳定高表达的细胞株HLFβ，以甲基甲磺酸（MMS）染毒，从DNA损伤、细胞周期及诱发突变等方面，研究pol-β在细胞应对DNA损伤时的作用。结果经过筛选获得人pol-β稳定高表达的细胞HLFβ，在MMS中、高剂量组（0．5～0．8mmol／L），MMS对HLFβ细胞的DNA损伤反应明显低于对照细胞，差异有统计学意义（P〈0．05）。细胞周期分析显示，MMS染毒后2种细胞在G2期均有阻滞现象。而在HLFβ组，当MMS剂量增加到0．5mmol／L时，除呸期阻滞外，49．0％的细胞被阻滞在G1期，而相同剂量下对照组只有20．1％阻滞于G1期。此外，在MMS 0．5mmol／L组，HLFβ与HLFC相比，诱发突变率从4．5×10^-6增加到8．2×10^-6差异有统计学意义（P〈0．05）。结论pol-β的高表达对细胞应对MMS的细胞毒性和遗传毒性具有一定的保护作用，其效应与HLFβ细胞周期G1期的阻滞有一定关系。但由于pol-β合成DNA的保真度较低，高表达的pol-β也增加了细胞突变的概率，可能产生远期遗传毒性。

Objeecive To investigate the biological effects of overexpression of the human DNA polymerase （pol-β） on cellular response to DNA damage. Methods The cell swain HLFβ from the stable overexpression of the human pol-β was contaminated with methyl methanesulfonate （MMS） for investigating the effects of the pol-β on the cellular responses to DNA damage on the aspects such as the DNA damage,the cell cycle and the induced mutation rate. Results The cell HLFβ from the stable overexpression of the human pol-β3 was obtained through the screening. The cellular response to DNA damage of HLFβ induced by the MMS in the intermediate and high dosage group （ranging from 0.5 to 0. 8 mmol/l,） was significantly lower than that in the control group, The analysis for the cell cycle distribution Mowed that both the two types of cells contaminated by MMS had retardation at Ca phase.In the HLFβ group,the cells had the obvious Ca phase retardation and 49.0% of the cells were retarded at G1 phase as well when the MMS was increased to 0.5 mmol/L while in the control, only 20.1% of the cells were retarded at the C1 phase when the same dosage of MMS was administered. Moreover, the MMS-indueed mutagenesis in HLFβ was increase, d from 4.5 × 10^-6 to 8.2 × 10^-6, significantly higher than that in the control group （P 〈0. 05）. Gonclusion High Pol-β level decreases cellular DNA damage induced by MMS. Nevertheless, the overexpression of Pol-β can also increase error-prone DNA synthesis during DNA repair process.