Stimulation of DNA-mediated transformation by UV irradiation of recipient (mouse FM3A) cells.

DNA-mediated transformation for thymidine autotrophs (Tk+) was stimulated severalfold when the recipient (mouse FM3A) (Tk-) cells were preirradiated by UV light. The effect was most prominently seen with the cells irradiated 12-16 hours prior to DNA addition. A similar stimulatory effect was observed when the cells were treated with novobiocin or mitomycin C. The effect, however, was blocked when cycloheximide was present during postirradiation period, suggesting that de novo protein synthesis is required for producing the effect. Most of the Tk+ transformants arised from the UV-irradiated cells carried the donor DNA sequences in their chromosomes.