Temperature-sensitive mutants of Balb/3T3 cells: description of a mutant affected in cellular and polyoma virus DNA synthesis.

A temperature-sensitive Dna- mutant (ts-2) of the mouse cell Balb/3T3 is characterized. Studies with synchronized cells indicate that the defect is in DNA synthesis itself, rather than in progress toward its initiation. ts-2 supports polyoma DNA synthesis after infection at 33degreesC but not at 38degreesC. Viral DNA synthesis begun at 33degreesC is inhibited upon shift to 38degreesC. A procedure is proposed by which viral DNA synthesis can be used to distinguish different classes of cell Dna- mutants.