OBJECTIVETo confirm the responses and function of hALP, a telomerase-regulation associated gene, in DNA damage.

METHODSHeLa and Hep2 cells were treated by genotoxic agents H2O2 and cisplatin, and the induced expression of hALP was measured by quantitative RT-PCR and immunofluorescent histochemistry. The alterations in transcriptional activity of hALP promoter were estimated by luciferase reporter assays. The effects of genotoxic agents on cells in different status of hALP expression were analyzed by MTT method.

RESULTSThe level of hALP mRNA could be increased when treated by 0.2 - 1.6 mmol/L H2O2 and reach a peak in concentration of 0.4 mmol/L. The induction could be observed after 6 h in the treatment of 0.4 mmol/L H2O2 and the higher level can be retained for 36 h. Similarly, cisplatin induced hALP mRNA expression is also dose and time dependent. The immunofluorescent staining showed that the treatment of 0.2 or 0.4 mmol/L H2O2, 0.2 or 0.5 micromol/L cisplatin increased the intensity of hALP protein in cellular nuclei. The luciferase assays demonstrated that both H2O2 and cisplatin could up-regulate hALP promoter activity through its upstream - 705 - +20 nt region. In cell survivor assay, the HeLa cells expressing sense hALP gene could grow continuously in the presence of 0.4 mmol/L H2O2 or 0. 5 micromol/L cisplatin while cells with antisense hALP or control cells were slower in growth.

CONCLUSIONSThe expression of hALP gene could be up-regulated by DNA damage through activating transcription of its promoter, and increase cellular resistance to genotoxic agents.