Takahashi S, Saito S, Ohtani N, Sakai T
Department of Preventive Medicine, Kyoto Prefectural University of Medicine, Japan.
Cancer Res. 2001 Feb 1;61(3):1187-95.
The gadd45 gene, a growth arrest and DNA damage (gadd)-induced gene, is transcriptionally activated by UV irradiation through two distinct pathways. One requires the sequence-specific binding of the p53 tumor suppressor protein to a responsive element within the third intron of the gadd45 gene, and the other is p53-independent activation of the gadd45 promoter region, although the UV-response element that mediates this has yet to be defined. 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-independent pathway.
gadd45基因是一种生长停滞和DNA损伤（gadd）诱导基因，通过两条不同途径在紫外线照射下被转录激活。一条途径需要p53肿瘤抑制蛋白与gadd45基因第三个内含子内的反应元件进行序列特异性结合，另一条途径是gadd45启动子区域的p53非依赖性激活，尽管介导此过程的紫外线反应元件尚未明确。为了研究在p53非依赖性途径中紫外线照射诱导gadd45的相关序列，我们在p53失活的细胞系中对与荧光素酶报告基因融合的人gadd45启动子进行了突变分析。我们发现紫外线反应元件涉及相对于转录起始位点-99 bp处的Oct-1结合位点。电泳迁移率变动分析表明，转录因子Oct-1结合gadd45基因上的该元件，尽管紫外线照射未改变阻滞条带的强度和迁移模式。这些结果表明，Oct-1调控元件可能是p53非依赖性途径中紫外线照射激活gadd45启动子所涉及的必需元件之一。
