Identification of a novel p53 promoter element involved in genotoxic stress-inducible p53 gene expression.

p53 is recruited in response to DNA-damaging genotoxic stress and plays an important role in maintaining the integrity of the genome. We show that exposure of cells to various genotoxic agents, including anticancer drugs such as mitomycin and 5-fluorouracil, results in an increase in p53 mRNA levels and in p53 promoter activation, indicating that the p53 genotoxic stress response is partly regulated at the transcriptional level. The results of the p53 promoter analysis show that a novel p53 promoter element, termed a p53 core promoter element (from -70 to -46), is essential for basal p53 promoter activity and promoter activation induced by genotoxic agents such as anticancer drugs and UV. Although a kappa B motif partially overlaps with this element and those genotoxic agents activate NF-kappa B, it does not play a major role in p53 genotoxic stress response: NF-kappa B p65 expression did not induce significant p53 promoter activation, and NF-kappa B inhibitors (N-acetyl cysteine and I kappa B alpha) did not inhibit genotoxic stress-inducible p53 promoter activation. Finally, we characterized nuclear factors, the binding of which to the p53 core promoter element is essential for basal p53 promoter activity and p53 promoter activation induced by genotoxic agents.