DNA infectivity and the induction of host DNA synthesis with temperature-sensitive mutants of simian virus 40.

Host DNA synthesis is induced when CV-1 (monkey kidney) cell cultures are infected at 40 C with wild-type virions or with temperature-sensitive Simian virus 40 mutants of the "early" complementation group A. Host DNA synthesis is not induced when cultures are infected with mutants of the late complementation group D. The simplest explanation for these observations, that induction depends not upon the expression of some early gene function but rather on the presence of an active D protein in the infecting virion, has been examined. Indirect experiments suggest that this explanation is not correct. Moreover, the induction of host DNA synthesis is impaired when cultures are infected with mutants of the A group at 42.5 C rather than 40 C, suggesting that the A function may be responsible for host induction. The inability of D virions to induce host DNA synthesis may reflect their inability to "uncoat" at 40C.