FIG. 3.

SDI-CL(NP) is selectively amplified in SAD Ambi-CAT-infected cells and interferes with HV replication. BSR cells were infected with SDI-CL(NP) stock and helper HVs, and passages (1.P, 2.P, and 3.P) were performed as described for Fig. 2. Cell RNA was analyzed with luciferase (A) and CAT (B) gene-specific DNA probes recognizing both plus- and minus-strand RNAs. Mini-RNA-derived luciferase mRNA was detectable in SAD Ambi-CAT-infected cells after the first passage, in contrast to SAD L16-infected cells. In SAD Ambi-CAT-infected cells, CAT RNAs are represented by a 1-kb monocistronic CAT mRNA, derived either from SDI-CL(NP) or from HV, a 3.1-kb RNA band composed of full-length mini-RNA and CAT/luciferase (luc) readthrough transcripts, and HV full-length RNA. The 3.1-kb hybridization signal was detectable after the first passage and much stronger after the second passage. At the bottom, the ratios of CAT mRNA and HV RNA are given.