A temperature-sensitive mutant of simian virus 40 affecting transforming ability

Abstract

In productive infection of monkey BSC-1 cells, ts 640, a temperature-sensitive (ts) mutant of simian virus 40 (SV40), was defective in its ability to synthesize infectious viral DNA and infectious viral particles at the restrictive temperature of 40 °, but not at the permissive temperature of 33 °. Growth of the mutant after infection with viral DNA was also temperature-sensitive, indicating that the block to multiplication at 40 ° is not due to failure in adsorption, penetration or uncoating. Results of mixed infections with other ts mutants showed that the gene identified in this mutant is different from those two cistrons which had been suggested to specify virion proteins. In nonproductive infection of rat 3Y1 cells, ts 640 was temperature-sensitive in its transforming ability at 40 ° but not at 33 °, providing evidence that cell transformation by SV40 is under the control of a viral gene function. The transformed cells obtained at 33 ° appeared not to revert to normal when shifted to 40 °, as judged from their colonial morphology under the standard culture conditions.