Distinct Biological Functions in Cancer and Development Regulate Transcription of Genes

The p63 gene shows remarkable structural similarity to the p53 and p73 genes. Because of two promoters, the p63 gene generates two types of protein isoforms, TAp63 and Np63. Each type yields three isotypes ( , , ) because of differential splicing of the p63 COOH terminus. The purpose of this study was to determine whether there is a functional link between the distinct p63 isotypes in their transcriptional regulation of downstream targets and their role in various cellular functions. TAp63 and Np63 adenovirus expression vectors were introduced into Saos2 cells for 4 and 24 h, and then gene profiling was performed using a DNA microarray chip analysis. Seventy-four genes (>2-fold change in expression) were identified that overlapped between two independent studies. Thirty-five genes were selected for direct expression testing of which 27 were confirmed by reverse transcription-PCR or Northern blot analysis. A survey of these genes shows that p63 can regulate a wide range of downstream gene targets with various cellular functions, including cell cycle control, stress, and signal transduction. Our study thus revealed p63 transcriptional regulation of many genes in cancer and development while often demonstrating opposing regulatory functions for TAp63 and Np63 .