Dark recovery of diploid yeast cells after simultaneous exposure to UV-irradiation and hyperthermia

Quantitative regularities of dark recovery of wild-type diploid yeast cells of Saccharomyces cerevisiae simultaneously treated with UV-light (254 nm) and high temperatures (53-56 degrees C) were studied. Under this combined action, the constant of recovery, which defines the probability of elimination of the UV-radiation induced damage per unit of time, did not depend on the temperature of irradiation. It was shown that both the irreversible component of cell damage and the number of cells that died without division gradually increased as the temperature of exposure increased. It is concluded, on this basis, that the mechanism of synergistic interaction of UV-radiation and hyperthermia is related not to the inhibition of dark recovery itself, but to the increase in the shape of irreversibly damaged cells incapable of recovering from the induced damage.