Mouse DDA3 gene is a direct transcriptional target of p53 and p73

The p53 tumor suppressor is a transcription factor that activates the expression of many target genes. We have previously reported the identification of a p53-regulated mouse gene DDA3. The 5' upstream genomic region of the mouse DDA3 was cloned, and sequence analysis revealed the presence of a potential p53 response element (RE2) residing at nucleotides +390 approximately +409 relative to the first translation start site. When fused upstream to a luciferase reporter gene, 5' genomic regions of the DDA3 gene containing RE2 were shown to be responsive to the wild-type, but not mutant p53, in a transient transfection assay. RE2 was sufficient to confer the transactivation responsiveness to p53. Furthermore, gel mobility shift analysis showed that RE2 formed specific complexes with wild-type p53. Induction of DDA3 was found in adriamycin treated normal mouse embryonic fibroblast cells (MEF), but not in p53 knockout (p53(-/-)) MEF. Overexpression of p73 induced DDA3 mRNA expression, and luciferase reporter analysis indicated that RE2 was responsive to transactivation by members of the p73 family proteins. Consistent with these findings, elevated expression of p73 protein and DDA3 mRNA were observed concomitantly in the p53(-/-) MEF cells treated with cisplatin. These results together demonstrated that DDA3 is a transcriptional target gene of p53 and its related-protein p73.