Induction and repair of DNA strand breaks and 1-beta-D-arabinofuranosylcytosine-detectable sites in 40-75 kVp X-irradiated compared to /sup 60/Co gamma-irradiated human cell lines
We have compared the initial yield and subsequent enzymatic repair of DNA strand breaks and 1-beta-D-arabinofuranosylcytosine (araC)-detectable sites in cultured human cell lines after irradiation with soft (40-75 kVp) X rays and hard (/sup 60/Co) gamma rays, two forms of low-LET radiation whose average ionization densities differ by 15-fold. Incubation of X- or gamma-irradiated cell cultures in the presence of araC resulted in the accumulation of DNA single-strand interruptions, as measured by conventional velocity sedimentation analysis in alkaline sucrose gradients. Since the drug is a selective inhibitor of DNA polymerase alpha, this observation implicates polymerase alpha in the repair of radiogenic damage. Specifically, DNA repair analysis in X-ray-treated cells suggested that polymerase alpha is a key participant in the repair of a distinct, albeit structurally undefined, class of radioproducts (presumably a combination of double-strand breaks and alkali-stable lesions, but takes little, if any, part in the restitution of single-strand breaks induced by ionizing radiation. Accordingly, the drug did not significantly inhibit the repair of DNA damage in cultures exposed to less than or equal to 100 Gy of gamma radiation. A remarkable difference was evident with respect to the absolute yields of these two major classes of DNA injury--that is, araC-detectable sites and single-strand breaks--depending on the type of radiation administered. For the same dose, the level of araC-detectable sites found in cells treated with gamma rays was as much as 3.4 times lower than that observed in X-ray-exposed cells.
- Research Organization:
- Cross Cancer Institute, Edmonton, Alberta (Canada)
- OSTI ID:
- 7195285
- Journal Information:
- Radiat. Res.; (United States), Vol. 114:1
- Country of Publication:
- United States
- Language:
- English
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ANIMAL CELLS
GENETIC RADIATION EFFECTS
STRAND BREAKS
DNA REPAIR
RADIOINDUCTION
CELL CULTURES
COBALT 60
COMPARATIVE EVALUATIONS
DNA
GAMMA RADIATION
IN VITRO
MAN
X RADIATION
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
COBALT ISOTOPES
ELECTROMAGNETIC RADIATION
GENETIC EFFECTS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONIZING RADIATIONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MAMMALS
MINUTES LIVING RADIOISOTOPES
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PRIMATES
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
RECOVERY
REPAIR
VERTEBRATES
YEARS LIVING RADIOISOTOPES
560120* - Radiation Effects on Biochemicals
Cells
& Tissue Culture