Fig. 7.

Mutational analysis of the termination-suppression signal (TSS) at the ORF1a/b junction. (A) Schematic view of the TSS expression construct and introduced HSV and HIS tags, showing only predicted RNA secondary structures that were consistent in the best six models generated by Mfold. Mutations around the stop codon (bold, producing the UAAA construct) or removing one side of the predicted stem-loops (Δ42) are shown. (B-D) Western blots showing translation of mutant TSS expression constructs in a coupled T7 polymerase rabbit reticulocyte lysate expression system. Blots were probed with anti-HSV (B, D) to detect both 25 kDa terminated and 32–35 kDa readthrough products, or with anti-HIS (C) to detect only readthrough products.