Schematic diagram of the PSIV genome, pT7CAT-5375, and the IRES region
of pT7CAT-5375. (A) Organization of the PSIV genome. The
open boxes and bold lines indicate coding and noncoding regions,
respectively. The numbers on the line represent nucleotide positions in
the PSIV sequence. (B) Organization of the dicistronic
plasmid, pT7CAT-5375, which contains the chloramphenicol
acetyltransferase (CAT) gene and the 5′ portion of the capsid protein
gene of PSIV. The thin line indicates the vector sequence, and the
triangle on the line represents the location of the T7 promoter
sequence. The thick line is the PSIV sequence. The numbers on the lines
represent nucleotide positions in the PSIV sequence. (C)
The predicted stem–loop structures (I–VI) upstream of the
capsid-coding region of PSIV. Mutations were introduced into the shaded
regions in stem–loop VI and in nucleotides 6190–6192. The base pair
interactions in the predicted pseudoknot between the loop of the
stem–loop structure (nucleotides 6163–6167) and the sequence just
upstream of the capsid-coding region (nucleotides 6188–6192) are
connected with a bold line.