FIG. 1.

Schematic illustration of DNA-based expression, genomic RNA replication, and sgRNA transcription of BMV RNA3 in yeast. “DNA” indicates a plasmid with RNA3 sequences (5′-UTR, 3a ORF, intergenic UTR with RE [black box], CP ORF, and 3′-UTR) flanked by the yeast GAL1 promoter and hepatitis δ virus ribozyme (Rz). Upon galactose induction, yeast RNA polymerase II synthesizes positive-strand RNA3 transcripts that, upon transport to the cytoplasm, serve as the templates for 1a- and 2a-dependent RNA3 replication and sgRNA transcription, which occur in 1a-induced ER membrane-associated replication compartments. Small white, black, and gray boxes indicate negative-strand, positive-strand, and sgRNA promoters, respectively.