A survey of DNA repair incision activities after ultraviolet irradiation of a range of human, hamster, and hamster-human hybrid cell lines.

We describe a rapid and simple assay for DNA damage and repair in mammalian cells, based on the partial unwinding of nicked DNA in alkali, and involving transfer of this DNA to nitrocellulose and the digestion of single-stranded DNA with S1 nuclease, all steps taking place on tissue-culture chamber slides. Direct breakage of DNA by ionizing radiation has been examined, and we have developed a standard procedure for measuring enzymic breakage of DNA as an index of excision-repair capacity following ultraviolet irradiation. We report a wide range of repair capacities among various hamster and human cell lines, with considerable overlap between the two species. Hybrids between hamster and human cells tend to display repair activity characteristic of the hamster parent.