Radiation Enhancement of the Efficiency of DNA-Mediated Gene Transfer in CHO UV-Sensitive Mutants

We have employed the Chinese hamster ovary (CHO) UV-sensitive mutant cell lines, UV5 and UV20, to determine whether ionizing and ultraviolet irradiation enhance the efficiency of DNA-mediated gene transfer in cells deficient in excision repair. Confluent AA8 (wild type), UV5, and UV20 cells were transfected (via polybrene and dimethyl sulfoxide treatments) with the recombinant DNA plasmid, pSV2-gpt, trypsinized, irradiated with either X rays or ultraviolet in suspension, and then plated into flasks. After a 48-h expression time, cells were trypsinized, counted, and plated in XMAT media to select for pSV2-gpt transformation. We report that X-ray irradiation enhances gene transfer in wild-type AA8 and in both UV-sensitive cell lines. Ultraviolet irradiation enhances gene transfer in AA8 and UV20, but not in UV5. Since both UV20 and UV5 are deficient in excision repair, we suggest that ultraviolet-enhanced gene transfer may involve a postreplication repair mechanism deficient in UV5.