Double-strand break repair and G2 block in Chinese hamster ovary cells and their radiosensitive mutants

Abstract

Two X-ray-sensitive mutants of the CHO K1 cell line were examined for their cell-cycle progression after irradiation with gamma-rays, and for their ability to rejoin double-strand breaks (DSBs) as detected by neutral filter elution. Both mutants were impaired in DSB rejoining and both were irreversibly blocked in the G2 phase of the cell cycle as determined by cytofluorometry. From one mutant we have isolated several revertants. The revertants stem from genomic DNA transfection experiments and may have been caused by gene uptake. All revertants survived gamma-irradiation as did the wild-type CHO line. One of them has been examined for its ability to rejoin DSBs and was found to be similar to the wild type.