Reparability of lethal lesions produced by phosphorus photoabsorption in yeast cells.
The characteristics of DNA lesions produced by the photoabsorption of phosphorus in yeast cells were studied using monochromatized soft X-rays tuned to the absorption peak of the phosphorus K-edge (2153 eV) and below the peak energy (2147 eV). The repaired fractions of DNA double-strand breaks (dsb) were measured relatively by using both a mutant, rad 54-3, which shows the temperature-sensitive dsb repair-deficient phenotype, and a wild-type strain. The repaired fraction of lesion in rad 54-3, which corresponds to the relative yield of dsb reparable by the RAD 54 pathway, was not affected by the phosphorus photoabsorption. Repair of the produced lesions in the wild-type cells was also measured by comparing the surviving fraction of the immediately plated cells to that of those cells plated after holding in a non-nutrient medium for 80 hrs. The recovery of the surviving fraction after the holding treatment was dependent upon the irradiated X-ray energy. These results suggest that irreparable lesions are produced by the inner-shell photoabsorption of phosphorus in DNA, although its yield is small.
Usami
N
N
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan.
Yokoya
A
A
Ishizaka
S
S
Kobayashi
K
K
D004260:DNA Repair / Q000502:physiology*; D010758:Phosphorus / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000528:radiation effects; D014965:X-Rays
D010758:Phosphorus