Transfer of a mutant viral thymidine kinase gene results in temperature-sensitive mouse cells

Temperature-sensitive cell lines were obtained by DNA-mediated transfer of the thymidine kinase (TK) gene from a mutant, ts1117, of herpes simplex virus type 1. The cells died at 39 degrees C in selective medium which contained low levels (1 microgram/ml) of thymidine. In this lethal condition, no revertants were detected among 10(8) cells. It was shown by in vitro analysis of the TK activity that the temperature-sensitive cell line contains an enzyme whose activity is temperature sensitive and relatively unaffected by dTTP. The viral enzyme has these properties. The effect of the lethal growth conditions in the cell line was characterized by cell cycle analysis and rescue experiments which involved a shift to the permissive conditions. The successful transfer of the mutant viral TK activity to cells provides an additional selective marker for gene transfer.