The expression of the P2Y₆ receptor is regulated at the transcriptional level by p53

Inflammatory bowel disease (IBD) is a risk factor for the development of colorectal cancer (CRC) for which mutation to p53 is an early event leading to dysplasia. Interestingly, P2RY6 mRNA increases in both pathologies. In this study, we investigated if p53 and p53^R273H mutant, commonly found in CRC and IBD, were involved in the transcriptional regulation of P2RY6. First, the P2RY6 promoter was defined as a region corresponding to -1600 to +273 nucleotides relative to the putative TATA-less transcriptional starting site found at position 73,264,505 of NCBI reference sequence NC_000010.11. We cloned this promoter region along with 5'-deletion constructs in the pGL4.10[luc2] vector for luciferase assays to delineate the minimal promoter region. We observed that p53 ^wt and p53^R273H differentially regulated the transcription of the P2RY6 gene. In fact, increasing quantity of p53^R273H enhanced the capacity of p53 ^wt to stimulate the transactivation of the P2RY6 promoter but this cooperative effect was lost when p53^R273H was present in a ratio of 3:1. In accordance with the luciferase assays, ChIP analysis revealed that endogenous p53 ^wt was significantly associated with the P2RY6 proximal promoter, whereas the interaction of the p53^R273H with the P2RY6 promoter was not significant. Although further studies are required to fully elucidate the molecular determinant controlling P2Y₆ expression in diseases, we propose, for the first time, a molecular mechanism involving a collaboration between p53 ^wt and p53^R273H to regulate the expression of this receptor.