Establishment of an experimental system to study p53 effects in Saccharomyces cerevisiae
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The aim of this vv^ork was to establish an experimental model to study human wild type and mutant p53 protein effects in yeast Saccharomyces cerevisiae cells. Wild type p53 was previously shown to be a DNA damage response gene that controls the genome stability in mammalian cells. We are interested in using yeast cells to study human p53-mediated cellular events after DNA damage. In this study we established an experimental model as an initial step. For construction of this system pAK31 plasmid expressing a human mutant p53-248W as well as control plasmid pL3 were used to obtain two different yeast cell populations, one expressing the mutant p53 248W protein and the other without p53 expression. Wild type p53 expression vector was avoided because of its known growth inhibitory effects in yeast cells. In this experimental system initially p53 expression at pAK31 transformed yeast cells was shown. Then, the effect of mutant p53-248W expression to growth rate of yeast cells was analysed and no growth rate difference was detected between the cells expressing and non-expressing mutant p53-248W protein. To test the participation of mutant p53-248W protein in DNA damage response in yeast cells, cells were exposed to DNA damaging agents; UVC and cisplatin that were reported to induce wild type p53 protein in mammalian cells. Codon 248 is a common site of ‘hot spot’mutation and the arginine residue that corresponds to codon 248 encoded by the wild type p53 sequence is in the DNA interacting face of the p53 protein. Mutant p53-248 (arg->trp) is defective in specific DNA binding and it has lost the ability to act as a transcription factor. Although there are not many reports about mutant p53-248W response to DNA damaging agents, it was shown that mutant p53- 248W exhibit decreased repair of active genes upon UV radiation. In this study cell survival was analysed in mutant p53-248W protein expressing yeast cells in parallel to mutant p53 protein levels following to DNA damage and no effect of mutant p53 248W expression on cell survival upon DNA damage was detected. Also no difference was detected in mutant p53 protein levels following DNA damage.