Mitchel R E, Morrison D P
Radiat Res. 1984 Oct;100(1):205-10.
Previous evidence in a lower eukaryote indicated the lack of an oxygen effect for ionizing radiation induction of radioresistance [P. E. Bryant, Nature (London) 261, 588-590 (1976)], suggesting that the signal for induction may be different from that in prokaryotes, where DNA damage by a variety of agents has been shown to induce SOS. type repair and radioresistance. We show here that prior exposure to a sublethal dose of gamma radiation caused induction of radioresistance in Saccharomyces cerevisiae, and that the rate of induction was proportional to the initial dose. Irradiation in oxygen produced a higher rate of increase in resistance, per unit dose, than irradiation in nitrogen, with an oxygen enhancement ratio of 2.8. The maximum level of resistance reached in response to saturating doses was the same regardless of the presence or absence of O2 during the initial irradiation. At less than saturating doses, however, the maximum increase in resistance was higher, per unit dose, following irradiation in the presence of O2 than in its absence. Oxic doses which gave the maximum possible in increase the level of resistance were considerably less than those required to produce the maximum rate of increase in resistance. These results suggest a difference in the level at which DNA damage saturates these processes. These results also indicate that the use of DNA damage as a signal for induction of radiation resistance has probably been conserved during the evolution of prokaryotes to lower eukaryotes.
先前在一种低等真核生物中的证据表明，电离辐射诱导抗辐射性不存在氧效应[P. E. 布莱恩特，《自然》（伦敦）261, 588 - 590（1976）]，这表明诱导信号可能与原核生物中的不同，在原核生物中，多种因素造成的DNA损伤已被证明会诱导SOS型修复和抗辐射性。我们在此表明，预先暴露于亚致死剂量的γ辐射会导致酿酒酵母中抗辐射性的诱导，且诱导速率与初始剂量成正比。与在氮气中辐照相比，在氧气中辐照每单位剂量产生的抗性增加速率更高，氧增强比为2.8。无论初始辐照期间是否存在O₂，响应饱和剂量所达到的最大抗性水平是相同的。然而，在低于饱和剂量时，每单位剂量下，在有O₂存在时辐照后的抗性最大增加量高于无O₂存在时。产生最大可能抗性水平增加的有氧剂量远低于产生最大抗性增加速率所需的剂量。这些结果表明DNA损伤使这些过程饱和的水平存在差异。这些结果还表明，在从原核生物到低等真核生物的进化过程中，可能一直保留了将DNA损伤用作诱导辐射抗性的信号的机制。
