Separation of lytic and transforming functions of the simian virus 40 A region: two mutants which are temperature sensitive for lytic functions have opposite effects on transformation.

Thirty-six of 40 rat cell clones transformed to anchorage independence at low multiplicity of infection by simian virus 40 tsA58 were heat sensitive for continued expression of the transformed phenotype. tsA1499 is an 81-base-pair deletion at 21 map units which is like tsA58 in that it is also heat sensitive for lytic growth, belongs to the A complementation group, and produces rat cell transformants which contain a thermolabile T antigen. Unlike tsA58, however, tsA1499 generated rat cell transformants efficiently at the temperature at which it was lytically defective, and 10 of 17 clones transformed by tsA1499 were cold rather than heat sensitive for the continued maintenance of the transformed phenotype. The lytic and transforming activities of the A region thus appeared to function independently in mutant tsA1499.