FIG. 4.

Mapping the 5′ boundary of IRES for PSIV capsid protein translation. (A) Schematic diagrams of pT7CAT-5375 and a series of deletion mutants. The thin lines indicate vector sequences, and the triangles represent the location of the T7 promoter. The thick lines indicate the PSIV sequence. The CAT genes and PSIV capsid-coding regions are shown by open and shaded boxes, respectively. The numbers above the lines indicate nucleotide positions. Deleted regions are shown by angled lines. (B) In vitro translation products of uncapped RNAs synthesized from pT7CAT-5375 and the deletion mutants shown in panel A. The positions of the translation products (CAT and capsid protein) are indicated on the right.