Co-dominance of radioresistant DNA synthesis in a group of AT-like Chinese hamster cell mutants

The relation of radiosensitivity 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 their parental V79 cells showed only very partial complementation of RDS, while radiosensitivity with respect to cell killing was fully complemented in these hybrid cells. Therefore, RDS behaves as a (co-)dominant feature in hybrids of AT-like mutants and wild-type V79 cells, indicating that RDS cannot be used for complementation analysis of X-ray-sensitive Chinese hamster cells. In contrast to the intraspecies hybrids, 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 afflicted gene.