FIG. 5.

Rescue of virus formation from transfected pMVM-E2F DNA in the presence of exogenous NS-1 proteins. A9 cells were transfected with pMVM or the mutant derivative pMVM-E2F alone or in combination with the NS-1-expressing plasmid pXNS1, incubated for 7 days, and collected. Progeny viruses were released, and their titers were determined by single-cell hybridization (A) and plaque assay (B), with A9 indicator cells. While viral DNA transfer is detected by the hybridization assay, the full infectivity of progeny virions is revealed by the plaque assay.