Recombination between temperature-sensitive mutants of simian virus 40

Seven temperature-sensitive (ts) SV40 mutants have been isolated and characterized. All of the mutants were defective in a late function. Four of the mutants were assigned to complementation group B, one to a new group designated C and two could not be assigned to a complementation group. Recombination occurred between mutants in the B and C complementation groups and between mutants in the B group. The recombination frequency (RF) between tsB302 and tsB306 was about 2.0 × 10^?4 when virus was used for infection, but was 10-fold higher when infectious ts SV40 DNAs were used. Treatment of doubly infected cells with 1-β-d-arabinofuranosylcytosine (ara-C) to interrupt DNA synthesis increased the RF 3- to 14-fold. Ultraviolet irradiation of viral inocula to 1–5% survival resulted in a 25- to 40-fold increase in RF. However, only a 2-fold increase in RF was obtained when uv-irradiated ts SV40 DNAs were used for infection. Ultraviolet irradiation of host CV-1 cells or pretreatment of host CV-1 cells with nonirradiated or uv-irradiated CV-1 DNA prior to infection failed to increase the RF between tsB302 and tsB306.