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CORRELATION BETWEEN CELL SURVIVAL AND DNA SINGLE‐STRAND BREAK REPAIR PROFICIENCY IN THE CHINESE HAMSTER OVARY CELL LINES AA8 AND EM9 IRRADIATED WITH 365‐nm ULTRAVIOLET‐A RADIATION
Author(s) -
CHURCHILL MARK E.,
PEAK JENNIFER G.,
PEAK MEYRICK J.
Publication year - 1991
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1991.tb03927.x
Subject(s) - chinese hamster ovary cell , biology , microbiology and biotechnology , dna repair , cell culture , irradiation , dna , genetics , physics , nuclear physics
— Cell survival parameters and the induction and repair of DNA single‐strand breaks were measured in two Chinese hamster ovary cell lines after irradiation with monochromatic UVA radiation of wavelength 365 nm. The radiosensitive mutant cell line EM9 is known to repair ionizing‐radiation‐induced single‐strand breaks (SSB) more slowly than the parent line AA8. EM9 was determined to be 1.7‐fold more sensitive to killing by 365‐nm radiation than AA8 at the 10% survival level, and EM9 had a smaller shoulder region on the survival curve (α= 1.76) than AA8 (α= 0.62). No significant differences were found between the cell lines in the initial yields of SSB induced either by γ‐radiation (as determined by alkaline sucrose gradient sedimentation) or by 365‐nm UVA (as determined by alkaline elution). For measurement of initial SSB, cells were irradiated at 0.5°C to minimize DNA repair processes. Rejoining of 365‐nm induced SSB was measured by irradiating cells at 0.5°C, allowing them to repair at 37°C in full culture medium, and then quantitating the remaining SSB by alkaline elution. The repair of these breaks followed biphasic kinetics in both cell lines. EM9 repaired the breaks more slowly (t 1/2 values of 1.3 and 61.3 min) than did AA8 (t 1/2 values of 0.9 and 53.3 min), and EM9 also left more breaks unrepaired 90 min after irradiation (24% vs 8% for AA8). Thus, the sensitivity of EM9 to 365‐nm radiation correlated with its deficiency in repairing DNA lesions revealed as SSB in alkaline elution. These results suggest that DNA may be a critical target in 365‐nm induced cellular lethality and that the ability of AA8 and EM9 cells to repair DNA strand breaks may be related to their ability to survive 365‐nm radiation.