The effect of factors causing induction of DNA breaks on transfection of chicken cells by the XC DNA, and the kinetics of appearance of virus-producing cells after transfection.

The effect of BUdR and 4NQO treatment of the recipient chicken fibroblast cultures on the efficiency of transfection by the XC DNA was investigated. The efficiency of transfection was 2-fold higher when the recipient cultures were incubated in the presence of 10 micrograms BUdR/ml in medium 199 (48%) than when cultures were not treated (25%). The efficiency was not further increased by exposure of BUdR-treated cultures to visible light for 20 min (31%). Growth of BUdR-treated cultures decreased after light irradiation which indicated that BUdR was incorporated into the host cell DNA. Treatment of the recipient cultures with 4NGO at a concentration of 0.4 micrograms/ml for 2 h before transfection exerted only unfavourable effects on transfection efficiency. In cultures positive in transfection, transformation was first detected 3 days after exposure to DNA by the infectious centre assay, with a frequency of 4.76 +/- 6.46 transformed cells per 10(6) cells.