Replication of the Resident Non-Defective SV40 in Transformed Human Cells Superinfected with DNA from a Temperature-sensitive SV40 Mutant

Abstract

SUMMARYParental and clonal lines of SV4o-transformed human embryonic lung (WI38 Va13A) cells spontaneously produce infectious virus which is temperature-resistant (tr), i.e. replicates in monkey kidney cells at either 38"7 °C or 33"5 °C. Superinfection of WI38 Va~3A cells lines with DNA from a temperature-sensitive (ts) SV4o mutant at the permissive temperature (33"5 °C) did not enhance the yield of tr SV4o as would be expected if the superinfecting ts SV4o DNA neutralized an SV4o-specific repressor, or if the ts SV4o DNA supplied a virus-specific excision function and/or post-excision functions for the maturation of the resident tr SV4o. The failure of superinfecting ts SV4o to enhance replication of the resident tr SV4o of WI38 VaI 3A cells is not due merely to a competitive advantage of the replicating superinfecting SV4 o over the endogenous SV4o. Experiments were carried out with ~-fl-o-arabinofuranosylcytosine (ara-C) treated and ts SV4o DNA-infected WI38 Va 13A cells to permit expression of early ts SV4o functions and to synchronize replication of ts SV4 o DNA and the newly excised endogenous SV4o DNA. Ara-C treatment did not enhance formation of the endogenous tr virus. In further competition experiments, CV-I cells were preinfected with ts SV4o particles and superinfected 6 to 24 h later with tr SV4o DNA recovered from SV4o spontaneously produced by WI38 VaI 3A cells. Even when the interval between the first and second infection was 24 b, very significant amounts of tr SV4o synthesis occurred and 28 ~ of doubly infected cells still produced temperature-resistant infectious centres. The experiments suggest that rescue of the resident SV4o is determined primarily by cellular rather than superinfecting SV4o gene functions.