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

Abstract

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. Key words: Ultraviolet ray; Jurkat cells; Methylation