CO-DOMINANCE OF RADIORESISTANT DNA-SYNTHESIS IN A GROUP OF AT-LIKE CHINESE-HAMSTER CELL MUTANTS

The relation of radiosensitivitv and radioresistant DNA synthesis (RDS ) was studied in the AT-like Chinese hamster cell mutants V-C4, V-E5, and V-G8 of the same complementation group. Proliferating hybrid cell lines obtained after fusion of the AT-like hamster cell mutants with t heir parental V79 cells showed only very partial complementation of RD S, while radiosensitivity with respect to cell killing was fully compl emented in these hybrid cells. Therefore. RDS behaves as a (co-)domina nt feature in hybrids of AT-like mutants and wild-type V79 cells, indi cating that RDS cannot be used for complementation analysis of X-ray-s ensitive Chinese hamster cells. In contrast to the intraspecies hybrid s, a full complementation of RDS was observed in interspecies hybrids between the rodent AT-like mutants and human (HeLa) cells, suggesting a species-specific regulation of DNA synthesis. These results indicate that radiosensitivity and RDS are pleiotropic effects of the same aff licted gene.