Characterization of temperature-sensitive mutants of SV40.

Abstract

SUMMARY We have isolated temperature-sensitive mutants of SV 40 in the lytic system by mutating the virus with nitrous acid or hydroxylamine, and characterized 11 of them. Nine mutants were grouped into two complementation classes in the productive infection of CV-1 cells. The first group contains a single mutant, which was defective in synthesizing virus DNA at the restrictive temperature, but induced the synthesis of cellular DNA. The mutants of the second class produced normal amounts of virus DNA and V-antigen at the restrictive temperature. A naturally-occurring large plaque strain belonged to this group. Both groups retained the transforming ability at the restrictive temperature. Two mutants showed no complementation with either group. One of them had the characters of the first group. The other mutant did not show temperature-sensitivity when the growth was initiated by infection with its DNA. This mutant did not transform 3T3 cells even at the permissive temperature. Rabbit kidney cells, however, were transformed by this mutant effectively at the permissive temperature but less at the restrictive.