The biological impact of the human master regulator p53 can be altered by mutations that change the spectrum and expression of its target genes

Human tumor suppressor p53 is a sequence-specific master regulatory transcription factor that targets response elements (REs) in many genes. p53 missense mutations in the DNA-binding domain are often cancer associated. As shown with systems based on the yeast Saccharomyces cerevisiae, p53 mutants can alter the spectra and intensities of transactivation from individual RE's. We address directly in human cells the relationship between changes in the p53 master regulatory network and biological outcomes. Expression of integrated, tightly regulated DNA-binding domain p53 mutants resulted in many patterns of apoptosis and survival following UV or ionizing radiation, or spontaneously. These patterns reflected changes in the spectra and activities of target genes, as demonstrated for P21, MDM2, BAX, and MSH2. Thus,as originally proposed for master genes of diversity, p53 mutations in human cells can differentially influence target gene transactivation, resulting in a variety of biological consequences which, in turn, might be expected to influence tumor development and therapeutic efficacy.