The effect of liquid-holding after γ and uv irradiation was investigated in three different strains of Schizosaccharomyces pombe: the haploid wild type $972\ {\rm h}^{-}$ , the diploid ${\rm h}^{-}/{\rm h}^{-}$ and the radiation-sensitive strain UVS-1 ${\rm h}^{-}$ . It was found that the diploid strain is only slightly more resistant to inactivation by both γ and uv irradiation compared to the haploid wild type. For liquid-holding experiments various non-nutrient solutions were examined and two which yielded minimal spontaneous cell death were chosen as favorable for all subsequent studies. These experiments have shown that: (i) the haploid wild type exhibited negative liquid-holding effect (NLHE) after γ irradiation, similar to that reported previously for uv irradiation; (ii) the diploid strain showed NLHE after both γ and uv irradiation; the rate of NLHE, for a given dose, was similar to that for the haploid strain; (iii) for both haploid an...

The Effect of Liquid Holding in Schizosaccharomyces Pombe Strains after Gamma and Ultraviolet Irradiation

Log-phase budding cells of two genetically marked diploid strains of S. cerevisiae are more resistant than nonbudding cells to x-ray-induced lethality and postirradiation lag, alterations in colony morphology associated with mitotic recombination, respiratory deficiency, and other nonlethal changes. The resistance of budding cells obtained from a nonbudding, small-cell population that had been stored in water at 6 to 8$sup 0$C overnight was intermediate between that of nonbudding and log-phase budding cells. Post-irradiation shifts in growth medium elicited repair of lethal and nonlethal damage in nonbudding and sensitive budding cells. Repair of lethal damage was greater in sensitive budding cells, and repair of nonlethal damage greater in nonbudding cells. Effects of budding and the medium shift in reducing lethality in sensitive budding cells were additive, while effects of budding and the shift on nonlethal damage were nonadditive. Normal budding cell resistance to x-ray lethality seems, therefore, to resemble the process elicited by medium shifts, unlike resistance to nonlethal damage. Only induced repair of lethal damage was actinomycin D sensitive. These and other observations, as well as several published but previously uncollated reports, suggest that budding cell resistance to x-ray lethality depends in part on efficient repair of chromosome breaks, and ismore » an adaptation for repairing damage in replicating DNA. (auth)« less

D.K. Myers

Papers

Protein and RNA synthesis in radiation-sensitive strains of yeast.