The Repair of Double-Strand DNA Breaks Correlates with Radiosensitivity of L5178Y-S and L5178Y-R Cells

Abstract

To better understand the basis for the difference in radiosensitivity between the variant murine leukemic lymphoblast cell lines L5178Y-R (resistant) and L5178Y-S (sensitive), the production and repair of DNA damage after X irradiation were measured by the DNA alkaline and neutral elution techniques. The initial yield of single-strand DNA breaks and the rates of their repair were found to be the same in both cell lines by the DNA alkaline elution technique. Using the technique of neutral DNA elution, L5178Y-S cells exhibited slightly increased double-strand breakage immediately after irradiation, most significantly at lower doses (i.e., less than 10 Gy). Nevertheless, even at doses that yielded equal initial double-strand breakage of both cell lines, the survival of L5178Y-S cells was significantly less than that of L5178Y-R cells. When the technique of neutral DNA elution was employed to measure the kinetics of DNA double-strand break repair, both cell lines exhibited biphasic fast and slow components of repair. However, the double-strand repair rate was much lower in the radiosensitive L5178Y-S cells than in the L5178Y-R cells (T1/2 of 60 vs 16 min). This difference was more pronounced in the fast-repair component. These results suggest that the repair of double-strand DNA breaks is an important factor determining the radiosensitivity of L5178Y cells.

Damage at two levels of DNA folding measured by fluorescent halo technique in X-irradiated L5178Y-R and L5178Y-S cells. II. Repair

“…The defect in DNA repair in LY-S (sensitive) cells, whicht could be expected from the pronounced susceptibility to tritiated compounds and the lack of a low dose-rate-sparing effect (Beer et al 1985), was demonstrated with pH 9.6 filter elution and premature chromatin condensation (Wlodek and Hittelman 1987). The earlier finding of slower repair of DNA strand breaks [alkaline sedimentation (Korner et al 1977)] was treated with some reservation because of the high (100 Gy) radiation dose applied.…”

Content of iron and copper in the nuclei and induction of pH 9-labile lesions in L5178Y sublines inversely cross-sensitive to H2O2 and x-rays

“…The high sensitivity of LY-S cells to x-rays (Do=0.5 Gy, Beer et al 1983) is reasonably explained by the impairment of double-strand break (DSB) rejoining (Wlodek and Hittelman 1987). An additional feature of LY-S cells is high initial DNA damage, estimated by neutral elution (Wlodek and Hittelman 1987) or by the fluorescent halo technique (Kapiszewska et al 1992). The radiation-resistant subline LY-R is H202-sensitive (Bouzyk et al 1991).…”

A DNA repair defect in a radiation-sensitive clone of a human bladder carcinoma cell line

“…The xrs, XR-1 and L5178Y-S mutants have been reported to show defective double-strand break (dsb) rejoining (Kemp et al, 1984;Giaccia et al, 1985;Evans et al, 1987;Wlodek & Hittelman, 1987) measured by neutral filter elution. The irs mutants have no measurable impairment of dsb rejoining, but irsl was found to have low repair fidelity compared with its parent line, V79, using plasmid reconstitution (Debenham et al, 1988b).…”