UVB对Jurkat细胞Gadd45a表达和DNA甲基化水平的影响

Effects of ultraviolet B （UVB） on the expression of Gadd45a gene and DNA methylation level in Jurkat cells

目的 探讨中波紫外线（UVB）对Jurkat细胞Gadd45a表达和DNA甲基化水平的影响.方法 分别以UVB 1.0 J/cm2和1.5 J/cm2照射Jurkat细胞后,于6、12、24、48 h收集细胞,采用实时定量RT-PCR法检测Gadd45a mRNA水平和甲基化敏感基因CD11a、CD70 mRNA水平,同时检测Jurkat细胞基因组DNA总体甲基化水平的变化.结果 ①和照射前Jurkat细胞比较,UVB 1.0 J/cm2照射后6、12、24、48 h Jurkat细胞Gadd45a mRNA水平升高,以照射后6、12 h差异有统计学意义（P＜0.01,P＜0.05）.UVB 1.0 J/cm2照射后,甲基化敏感基因CD11a、CD70 mRNA水平也升高,以照射后12 h差异有统计学意义（P值均＜0.05）.②以UVB 1.5 J/cm2照射Jurkat细胞,和照射前Jurkat细胞比较,照射后6、12、24、48 h,Jurkat细胞Gadd45a、CD11a、CD70 mRNA水平均显著升高（P＜0.05或P＜0.01）.③和照射前Jurkat细胞比较,Jurkat细胞经UVB 1.0 J/cm2照射后6、12、24、48 h总体甲基化水平降低,照射后6、12 h甲基化水平差异有统计学意义（P＜0.05,P＜0.01）.Jurkat细胞经UVB 1.5 J/cm2照射后6、12、24、48 h的总体甲基化水平显著降低,差异均有统计学意义（P值分别＜0.01、＜0.01、＜0.01、＜0.05）.④UVB照射后Jurkat细胞的Gadd45a mRNA和DNA总体甲基化水平呈显著负相关（r=-0.395,P＜0.05）.结论 UVB能诱导Jurkat细胞Gadd45a表达上凋,同时Jurkat细胞基因组DNA发生低甲基化.

Objective To explore the effects of UVB on the expression of Gadd45a gene and DNA methylation levels in Jurkat cells. Methods Jurkat cells were irradiated with UVB of 1.0 J/cm2 and 1.5 J/cm2 respectively, and collected at 6, 12, 24 and 48 hours after the irradiation. Real-time RT-PCR was used to detect the mRNA expression of Gadd45a gene and methylation-sensitive genes CD11a and CD70. Global methylation level was also measured by MethylAmp global DNA methylation quantification kit. Results After irradiation with UVB at 1.0 J/cm2, the mRNA level of Gadd45a increased but global methylation level decreased at 6, 12, 24 and 48 hours, and significant changes were observed at 6 and 12 hours for the level of both Gadd45a mRNA expression and global methylation （P ＜ 0.01 or 0.05）. Elevated mRNA expressions of CD11 a and CD70 were also noted in Jurkat cells after irradiation with UVB of 1.0 J/cm2, and significant elevation was observed at 12 hours （both P ＜ 0.05 ）. After irradiation with UVB of 1.5 J/cm2, there was a statistical increase in the mRNA expressions of Gadd45a, CD11 a, CD70, together with a statistical decrease in global methylation level in Jurkat cells, at 6, 12, 24 and 48 hours （P ＜ 0.01 or 0.05）. The mRNA expression of Gadd45a negatively correlated with the global level of DNA methylation in Jurkat cells （r = -0.395, P ＜ 0.05）. Conclusion UVB irradiation can upregulate the expression of Gadd45a, but downregulate the global DNA methylation level in Jurkat cells.