Effects of overexpression of human pol-beta on cellular response to DNA damage / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the biological effects of overexpression of the human DNA polymerase (pol-beta) on cellular response to DNA damage.</p><p><b>METHODS</b>The cell strain HLFbeta from the stable overexpression of the human pol-beta was contaminated with methyl methanesulfonate (MMS) for investigating the effects of the pol-beta on the cellular responses to DNA damage on the aspects such as the DNA damage, the cell cycle and the induced mutation rate.</p><p><b>RESULTS</b>The cell HLFbeta from the stable overexpression of the human pol-beta was obtained through the screening. The cellular response to DNA damage of HLFbeta 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 showed that both the two types of cells contaminated by MMS had retardation at G(2) phase. In the HLFbeta group, the cells had the obvious G(2) phase retardation and 49.0% of the cells were retarded at G(1) 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 G(1) phase when the same dosage of MMS was administered. Moreover, the MMS-induced mutagenesis in HLFbeta was increased from 4.5 x 10(-6) to 8.2 x 10(-6), significantly higher than that in the control group (P < 0.05).</p><p><b>CONCLUSION</b>High Pol-beta level decreases cellular DNA damage induced by MMS. Nevertheless, the overexpression of Pol-beta can also increase error-prone DNA synthesis during DNA repair process.</p>

Effects of hydroquinone on DNA and nucleus damage in human embryo lung fibroblasts / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study DNA and nucleus damage in human embryo lung fibroblast (HLF) exposed to hydroquinone (HQ) and its genotoxicity.</p><p><b>METHODS</b>HLF were treated with HQ (0, 10, 20, 40, 80 micro mol/L, respectively) for 3 h and DNA damage was detected by comet assay. HLF was also treated with the same concentrations of HQ for 1 h and micronucleus test was performed after they were cultured for 24 h.</p><p><b>RESULTS</b>Comet assay showed that percentage of cells with tails in each groups treated with varied doses of HQ was 12%, 19%, 42%, 79% and 95%, respectively, with mean tail length of 7.87, 9.35, 11.03, 19.28 and 23.32 micro m, respectively, in an obvious dose-dependent manner (P < 0.05). Very significant increase in percentage of cells with tails and length of their comet tail were observed in those groups treated with HQ of 20, 40 and 80 micro mol/L (P < 0.01). And, proportion of high and severe DNA damage increased with dose of HQ. HQ could also induce formation of micronucleus and abnormal nucleus in all groups treated by varied doses of HQ, with rates of micronucleus and abnormal nucleus of 2%, 3%, 10%, 9% and 15%, and 6%, 7%, 16%, 27% and 28%, respectively, in a significant dose-dependent manner. There was significant increase in rates of micronuclei and abnormal nuclei in cells treated with HQ at doses of 20, 40 and 80 micro mol/L (P < 0.05).</p><p><b>CONCLUSIONS</b>Exposure to HQ could cause DNA and nucleus damage inducing genotoxic effects on HLF.</p>

Construction of eukaryotic expression vector of hMTH1 gene antisense RNA / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To construct pEGFP-C1-T vector, an eukaryotic expression plasmid of hMTH1 gene antisense RNA.</p><p><b>METHODS</b>The conservative region of hMTH1 gene was amplified by RT-PCR after total RNA being extracted from human embryo lung fibroblast (HLF) and then cloned into pGEM-T vector. After the recombinant plasmid was certified by DNA sequencing, the conservative region of hMTH1 gene was inserted into pEGFP-C1 vector reversedly and pEGFP-C1-T vector was constructed. The efficiency of antisense inhibition was verified by Western blotting after cell transfection.</p><p><b>RESULTS</b>423 bp fragment including conservative region of hMTH1 gene was obtained by RT-PCR. After cloned by pGEM-T vector and certified by DNA sequencing, pEGFP-C1-T vector was successfully constructed by means of recombinant DNA technology. Additionally pEGFP-C1-T vector could efficiently decrease hMTH1 protein level by 46%.</p><p><b>CONCLUSION</b>The efficient expression vector of hMTH1 gene antisense RNA, pEGFP-C1-T has been constructed successfully.</p>