FIG. 4.

Effects of frameshift mutations on 2a ORF-dependent 1a responsiveness. (A) On the left are schematic diagrams of G2aA and its frameshift derivatives. The number of nucleotides inserted (i) or deleted (Δ) and their position (*) in RNA2 as well as the resulting number of in-frame 2a codons (preceding +) and out-of-frame codons (following +) translated are indicated. Membrane association abilities of these RNAs in the absence (−1a) or presence (+1a) of 1a were assessed by cell fractionation to measure RNA distribution in the pellet (P) and supernatant (S) fractions as described in the legend to Fig. 1. Representative Northern blots are shown. As a measure of 1a responsiveness, the difference between the percentages of pelletable RNA in the presence and the absence of 1a was calculated for each RNA. The data shown are averages from three or more independent experiments for each derivative. (B) Comparison of the 1a responsiveness of matched frameshift and in-frame insertion mutations, which differ by only a single nucleotide. (C) Western blotting of total protein extracts from yeast harboring each of the G2aA derivatives shown in panels A and B.