p53--a key player in tumoral and evolutionary adaptation: a lesson from the Israeli blind subterranean mole rat.

p53 is a transcription factor involved in maintaining genomic integrity by regulating genes involved in cell cycle arrest, DNA repair, and programmed cell death. Various post transcriptional modifications result in activated p53 with varying binding affinity to its targets. The other members of the p53 family (p63, p73) and associated proteins also contribute to the specificity of gene activation resulting in the final cell responses. p53 is commonly mutated in human cancer and is activated by diverse cellular events, including hypoxia. Many sources of genetic diversity, including random or stress-related mutagenesis, affect normal species evolution. The blind subterranean mole rat lives in sealed underground tunnels, subjected to routine hypoxia due to abrupt and sharp changes in O2 supply. We cloned the mole rat's p53 gene and identified two amino acid substitutions in its binding domain, in the same positions that are mutated in cancer. These substitutions lead to increased p53 activation of DNA-repair elements and reduced activation of apoptotic genes. We propose that sequence-specific changes in the mole rat's p53 gene provide an example of how transcription factors that regulate many genes can also account for rapid and broad phenotypic diversity by altering the binding affinity to individual target genes.