Identification of vitamin D receptor as a target of p63

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Abstract
P63, a p53 homolog has been shown to play a role in development and cancer. p63 is essential for both commitment of ectoderm to stratified epithelia and for the proliferative potential of epithelial stem cells. p63 knockout mice are born with severe development defects and lack organs of epithelial origin. In addition, p63 has also been shown to play a role in cancer development through the differential regulation of genes with tumor suppressor function and genes involved in metastasis. In order to understand the role of p63 in cancer and development, genes that are specifically regulated by p63 but not p53 were identified. In this study, we provide evidence that p63 specifically upregulates vitamin D Receptor (VDR). In contrast, p53 does not appear to be involved in upregulation of VDR expression. Additionally, we demonstrate that a naturally occurring p63 missense mutant, p63 (R279H) and p14ARF, both act in a dominant negative manner to inhibit p63-mediated upregulation of VDR. Furthermore, using chromatin immunoprecipitation assays, we demonstrated that p63 directly binds to the VDR promoter in vivo. Our findings clearly demonstrate that VDR is a direct target of p63 and suggests that p63 may play a role in cancer and differentiation through modulation of the VDR pathway.