The p53 Family Member Genes Are Involved in the Notch Signal Pathway

Abstract

The p53 tumor suppressor is a transcription factor that regulates cell growth and death in response to environmental stimuli such as DNA damage. p63/p51 and p73 were recently identified as members of the p53 gene family. In contrast to p53 however, p63 and p73 are rarely mutated in human cancers. Mice that lack p53 are developmentally normal, while p63 and p73 appear to play critical roles in normal development. To determine how p63 and p73 are involved in normal development, we attempted to identify target genes that are specifically regulated by p63 and/or p73 but not by p53. We found that the Jagged1 (JAG1) and Jagged2 (JAG2) genes, encoding ligands for the Notch receptors, are up-regulated by p63 and p73. Furthermore, we identified a p63-binding site in the second intron of the JAG1 gene, which can directly interact with the p63 protein in vivo, as assessed by a chromatin immunoprecipitation assay. A heterologous reporter assay revealed that this p63-binding site is a functional response element and is specific for p63. We also found a target of Notch signaling, HES-1 was up-regulated in Jurkat cells, in which Notch1 is highly expressed, when co-cultured with p63-transfected cells, suggesting that p63 can trigger the Notch signal pathway in neighboring cells. Our findings show an association between the p53 family genes and Notch signaling and suggest a potential molecular mechanism for the involvement of the p53 family genes in normal development.The involvement of the p53 tumor suppressor gene in cell growth and death is mediated by the transactivation of p53-target genes in response to environmental stimuli such as DNA damage (1-3). p63/p51 and p73 were recently identified as members of the p53 gene family and encode proteins that share considerable structural homology with p53 (4 -6). p63 and p73 can bind to the p53-responsive elements and up-regulate some p53-target genes, which suggest that the p53 family members have a potential for functional overlap with p53 itself (7-12). However, in contrast to p53, p63 and p73 are rarely mutated in human cancers (13)(14)(15).Different phenotypes between p63-or p73-deficient and p53-deficient mice were also reported (16 -19). In contrast to p53-deficient mice, mice lacking the p73 genes show no increased susceptibility to spontaneous tumorigenesis. p73-deficient mice have neurological, pheromonal and inflammatory defects. p63-deficient mice have major defects in their limbs and craniofacial development, as well as a striking absence of stratified epithelia, suggesting that p63 is required for limb and epidermal morphogenesis. In humans, Li-Fraumeni syndrome patients have inherited mutations of the p53 gene and develop normally, but are predisposed to cancer (20), while heterozygous germline mutations in the p63 gene are the cause of ectrodactyly, ectodermal dysplasia, and facial clefts syndrome (21). These studies demonstrate a marked divergence in the developmental roles of p63 and p73 and further distinguished these p53 family genes from p53. Despite these revel...

p63 consensus DNA-binding site: identification, analysis and application into a p63MH algorithm

“…In the p63 ChIP, we observed significant enrichment for the putative PTPN14 and ING1 REs relative to background (Figure 4b). Constitutive p63 binding was also observed at the known p63-responsive elements p21 site 1 (Westfall et al, 2003) and JAG1 (Sasaki et al, 2002). After ADR treatment, p63 binding to all four REs decreased.…”

“…JAG1 is a notable example of genes exhibiting p63-mediated upregulation, but not p53-mediated transactivation (Sasaki et al, 2002). Genes displaying p63 but limited p53 responsiveness included, but were not limited to, ING1, a tumor suppressor involved in cell cycle arrest, DNA repair and apoptosis (Campos et al, 2004) and PTPN14, a phosphatase involved in cell-cell adhesion and cellular migration (Wadham et al, 2003).…”

“…(b) REs found in genes differentially regulated by ectopic TAp63g and p53. The JAG1 sequence has been reported previously (Liu and Chen, 2002;Sasaki et al, 2002). The candidate REs for ING1 (chr13:110164845-110164869; þ strand) and PTPN14 (chr1:211001383-211001403; À strand) were selected using the algorithm p63MH.…”

Identification of vitamin D receptor as a target of p63

“…Expression of Maspin, a tumor suppressor gene, has also been shown to be positively regulated by p63 in lung cancer specimens (Kim et al, 2004;Spiesbach et al, 2005). Similarly, both Jagged 1 and Jagged 2, ligands of the Notch receptor known to play a role in tumor development, are specifically induced by p63 but not p53 (Sasaki et al, 2002a). Similar to p53, p63 has also been shown to activate major apoptosis pathways by triggering signaling via death receptors and the mitochondria (Gressner et al, 2005).…”

Proliferation and cornification during development of the mammalian epidermis

“…p300 directly interacts with pTA63␥ at its N-terminus and stimulates pTA63␥-dependent transcription and induction of p21 WAF/Cip1 in vitro (Macpartlin et al, 2005). Interestingly, in vitro studies have shown that the Notch ligand, Jagged1 (JAG1), is a direct target of pTA63␥ (Sasaki et al, 2002). This observation suggests a direct link between p63 and Notch signaling in epidermal development (Fig.…”