Isolation of Chinese hamster ovary cells with reduced unscheduled DNA synthesis after UV irradiation.

A simple procedure has been worked out to obtain UV-sensitive mutants of Chinese hamster ovary (CHO) cells. In this procedure, conventional mutagenesis is followed by BrdU--light treatment to enrich the population for UV-sensitive cells. Colonies that are allowed to form subsequently are duplicated by replica plating and screened on the master plate for their UV sensitivity and their capacity to carry out UV-induced DNA repair synthesis. Putative mutants are isolated from the replica. With this combination of methods, we succeeded in isolating CHO mutants with an 85-95% reduced level of UV-induced DNA synthesis in combination with an increased UV sensitivity.