Enhancement of genetic transformation frequencies of mammalian cell cultures by damage to the cell DNA.

Ultraviolet (UV)-light and 5-fluorodeoxyuridine (FUdR), two known DNA damaging agents, were found to enhance the frequency of stable plasmid transformations in several different animal cell lines. Combined treatment with the two agents was more effective than treatment with either agent alone. A correlation between the transformability of a cell line in the absence of treatment and its response to damaging treatment was also observed. Southern blot analysis of transformed clones indicated that the stimulation in transformation frequency was not due to an increased number of copies of the integrated plasmid in the transformed cells.