FIG. 4.

Detection of vector minus-strand and plus-strand RNA by RT-PCR. The cDNA corresponding to either minus strand or plus strand was amplified using strand-specific primers from total RNA of either BHK cells lines containing the cloned variants (S1 and SF2C) or naive BHK cells electroporated 24 h earlier with the parental vectors (SINBV and SFV). As an internal control, the housekeeping BHKp23 mRNA was amplified from each sample (p23). Amplification mixtures were divided into six aliquots, and one aliquot per sample was removed after 5, 10, 15, 20, 25, and 30 amplification cycles, as indicated above the lanes. Images were processed with Adobe Photoshop software.