An eighth complementation group of rodent cells hypersensitive to ultraviolet radiation

Two mutant lines (US31, US46) of mouse lymphoma cells that are hypersensitive to ultraviolet (UV) radiation were previously found to belong to different complementation groups. The mutants were tested for their ability to complement the six known complementation groups of UV-sensitive Chinese hamster ovary (CHO) cells, which are defective in nucleotide excision repair, as well as a seventh group represented by a V79 mutant. Hybrid cells were produced by fusion with polyethylene glycol and tested in situ for UV resistance. The mouse mutant US46 complemented all CHO mutants except UV61. Therefore, US46 is assigned to the same complementation group as UV61, and it is probably defective in the same locus. The mouse mutant US31 produced UV-resistant hybrid cells in each of the seven crosses, indicating that it forms an eighth complementation group among the rodent mutants. Thus, at least eight genes are likely required to repair UV damage in rodent cells.