Development of specific prevention against DNA damage caused by environment

gadd45基因通过p53依赖性或p53非依赖性途径在紫外线照射下转录激活。为了研究在p53非依赖性通路中，紫外线照射诱导gadd45的序列，我们对p53失活的细胞系中与荧光素酶报告基因融合的人类gadd45启动子进行了突变分析。我们发现，uv响应元件参与了相对于转录起始位点-99 bp的Oct-1结合位点。电泳迁移率转移实验表明，转录因子Oct-1将该元件结合在gadd45基因上，但紫外线照射并未改变其迁移带的强度和模式。这些结果表明Oct-1调控元件可能是参与紫外线照射激活gadd45启动子的p53非依赖性途径的重要元件之一。组蛋白去乙酰化酶（HDAC）抑制剂已被发现可导致多种肿瘤细胞在G1和/或G2/M期生长停滞、分化和/或凋亡。我们证明，gadd45，已被证明导致细胞周期阻滞在G2/M期并参与基因毒性应激诱导的细胞凋亡，也可以由典型的HDAC抑制剂trichostatin a （TSA）通过其启动子以p53独立的方式诱导。为了确定gadd45启动子的激活机制，我们进行了荧光素酶报告基因分析和电泳迁移转移实验。对gadd45启动子的分析表明，Oct-1和CCAAT位点都是TSA完全激活所必需的。我们还发现转录因子Oct-1和NF-Y特异性地结合在每个位点上。我们的研究结果表明，HDAC抑制剂可以通过gadd4S的启动子诱导gadd4S，而不需要功能性p53， Oct-1和NF-Y共同参与tsa诱导的gadd45启动子的激活。

The gadd45 gene is transcriptionally activated by UV irradiation through p53-dependent or p53-independent pathways. To investigate the sequences involved in induction of gadd45 by UV irradiation in a p53-independent pathway, we performed mutation analyses of the human gadd45 promoter fused to the luciferase reporter gene in cell lines in which p53 was inactivated. We found that the UV-responsive element was involved in the Oct-1 binding site at -99 bp relative to the transcription start site. Electrophoretic mobility shift assays showed that Oct-1, a transcription factor, bound this element on the gadd45 gene, although the intensity and mobility pattern of the retarded bands were not altered by UV irradiation. These results suggest that the Oct-1 regulatory element might be one of the essential elements involved in the activation of the gadd45 promoter by UV irradiation in a p53-indepeadent pathway.Histone deacetylase (HDAC) inhibitors have been revealed to cause growth arrest at G1 and /or G2/M phases, differentiation, and/or apoptosis in a wide variety of tumor cells. We demonstrated that gadd45, which has been shown to cause cell cycle arrest at G2/M phase and take part in genotoxic stress-induced apoptosis, is also induced by a typical HDAC inhibitor, trichostatin A (TSA), through its promoter in a p53-independent manner. To identify the mechanism of activation of the gadd45 promoter, we performed luciferase reporter analyses and elecrophoretic mobility shift assays. Analysis of the gadd45 promoter revealed that both the Oct-1 and CCAAT sites are needed for the full activation by TSA. We also found that transcription factors, Oct-1 and NF-Y, specifically bind to each site. Our results suggest that HDAC inhibitors can induce gadd4S through its promoter without functional p53 and both the Oct-1 and NF-Y concertedly participate in TSA-induced activation of the gadd45 promoter.