ycf and yap gene expressions in yeast cells after irradiation combined with mercury treatment

background: all aerobically growing organisms suffer from exposure to oxidative stress, caused by partially reduced forms of molecular oxygen, known as reactive oxygen species (ros). these are highly reactive and capable of damaging cellular constituents such as dna, lipids and proteins. consequently, cells from many different organisms have evolved mechanisms to protect their components against ros. it is known to have some genes for resistance to heavy metals and ionizing radiation (ir). materials and methods: saccharomyces cerevisiae is an ideal model organism for deducing biological processes in human cells. in this work, cell viability and gene expression was investigated in yeasts treated with ir, hgcl2, and ir combined with hgcl2. cell viability was measured by colony forming unit (cfu) method in an ypd medium. gene expression was analyzed by the real-time pcr. results: the viability was lower at the higher dose. at a dose above a certain level, the viability came down to zero. the combined treatment decreased the viability, as well. metal resistance genes were expressed in the cells treated with hgcl2. in a similar way, irradiation also triggered the expression of some radiation resistance genes. ycf and yap genes were induced consecutively with the hgcl2 concentration, and also with a higher total dose under a lower dose rate condition. these two genes were, however, expressed differently under the 0.2 mm hgcl2 treatment condition. in the cells treated with 0.1-0.2 mm hgcl2, the viability was higher than with any other concentrations. conclusion: the results demonstrated that the higher dose induced more expression of oxidative stress resistance genes related to cell survival mechanism. combined treatment of radiation with mercury chloride resulted in synergistic effects leading to a higher expression of the genes than treatment of a single stressor alone. iran. j. radiat. res., 2009 6 (4): 161-166