Mutation induction in haploid yeast after split-dose radiation exposure. II. Combination of UV-irradiation and X-rays

• Published in: Environmental and molecular mutagenesis Vol. 43; no. 1; pp. 28 - 35
• Main Authors: Keller, B., Zölzer, F., Kiefer, J.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 2004; Wiley-Liss
• Subjects: antagonism; Biological and medical sciences; canavanine resistance; Cell Culture Techniques; Cell Survival - radiation effects; Dose-Response Relationship, Radiation; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Haploidy; inducible repair; Medical sciences; Mutation; mutation induction; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - radiation effects; synergism; Time Factors; Toxicology; ultraviolet radiation; Ultraviolet Rays; X-Rays; yeast; Yeast; Induction; X-rays; inducible repair; Exposure; X ray; canovanine resistance; X ray irradiation; Synergism; mutation induction; Resistance; Antagonism; Radiation dose; Ultraviolet radiation; Ultraviolet irradiation; Genetics; Mutation; Repair
• ISSN: 0893-6692; 1098-2280
• DOI: 10.1002/em.10206

Split‐dose protocols can be used to investigate the kinetics of recovery from radiation damage and to elucidate the mechanisms of cell inactivation and mutation induction. In this study, a haploid strain of the yeast, Saccharomyces cerevisiae, wild‐type with regard to radiation sensitivity, was irradiated with 254‐nm ultraviolet (UV) light and then exposed to X‐rays after incubation for 0–6 hr. The cells were incubated either on nutrient medium or salt agar between the treatments. Loss of reproductive ability and mutation to canavanine resistance were measured. When the X‐ray exposure immediately followed UV‐irradiation, the X‐ray survival curves had the same slope irrespective of the pretreatment, while the X‐ray mutation induction curves were changed from linear to linear quadratic with increasing UV fluence. Incubations up to about 3 hr on nutrient medium between the treatments led to synergism with respect to cell inactivation and antagonism with respect to mutation, but after 4–6 hr the two treatments acted independently. Incubation on salt agar did not cause any change in the survival curves, but there was a strong suppression of X‐ray‐induced mutation with increasing UV fluence. On the basis of these results, we suggest that mutation after combined UV and X‐ray exposure is affected not only by the induction and suppression of DNA repair processes, but also by radiation‐induced modifications of cell‐cycle progression and changes in the expression of the mutant phenotype. Environ. Mol. Mutagen. 43:28–35, 2004. © 2004 Wiley‐Liss, Inc.