YEAST AS A MODEL FOR THE STUDY OF HUMAN p53

The p53 tumor suppressor gene is a major barrier against cancer, preventing tumor development and promotes apoptosis induced by chemotherapy. P53 is able to regulate apoptosis both through its transcriptional activity and by the induction of the outer mitochondrial membrane (OMM) permeabilization promoting the release of cytochrome c. In the yeast S. cerevisiae, the machinery of the basic apoptotic process seems to be conserved as it presents many of the cytological markers of apoptosis such as chromatin condensation, DNA fragmentation and the release of cytochrome c from mitochondria to the cytoplasm. It was recently reported that the expression of p53 in S. cerevisiae is able to activate the apoptotic processes, making this system a good model to analyze the basic mechanisms of apoptosis induced by p53. It was recently identified a novel mutation in p53, in which lysine 351 is replaced by an asparagine (K351N) in a cisplatin-resistant ovarian carcinoma cell line (A2780 CIS). The K351N mutation is associated with the acquisition of resistance to apoptosis induced by cis-platinum in this cell line. The K351N mutation significantly reduces the thermodynamic stability of p53 tetramers, the transcriptional activity of p53 and affects the export from the nucleus to the cytosol induced by cisplatinum treatment. The characterization of this mutant could thus help to envisage the development of new cancer drugs that can suppress this phenotype in tumors. We cloned the two human genes, p53 and its mutated form p53K351N, under the control of Gal1-Gal10 vector and we transformed them in both wild type and S. cerevisiae strains mutated in genes involved in the apoptotic response. We then analyzed the effect of the p53 expression during an apoptotic stimulus (H2O2) and during aging.