Identification of a specific target sequence for p53 family in the Jagged2 gene

Inactivation of the tumour suppressor p53 is the most common defect in cancer cells. The p53 family members, p73 and p63, have remarkable structural similarities with p53 and can activate transcription of p53-responsive genes. In contrast to p53 however, p73 and p63 are rarely mutated in human cancers. Mice that lack p53 are developmentally normal, while p73 and p63 appear to play critical roles in normal development. In our earlier study, we showed that both p73 and p63 regulate the ligands for the Notch receptor, Jagged1 (JAG1) and Jagged2 (JAG2). We also identified a p63-binding site in the second intron of the human JAG1 gene. Here, we have analyzed the responsive element within the human JAG2 gene for p73/p63-dependent induction of gene expression. Using a chromatin immunoprecipitation assay, we identified a p73/p63-binding site located in the second intron of the JAG2 gene. A heterologous reporter assay revealed that this binding site is a functional response element and is relatively specific for p73 and p63 among the p53 family. This binding site consists of four copies of 10-bp consensus p53-binding motif and is highly conserved between human and rodents. Furthermore, both JAG1 and JAG2 mRNA were specifically up-regulated by either p63 or p73, but not by p53 in mouse embryo fibroblasts. Our findings demonstrate that JAG2 is indeed a direct and evolutionarily conserved transcriptional target of p73 and p63, and suggest a potential molecular mechanism for the involvement of the p53 family genes in normal developmen