Secondary structures and starvation‐induced frameshifting

We have examined the effect of a downstream secondary structure (the stem–loop sequence found downstream on the MMTV gag‐pro frameshift site) on frameshifting at a bacterial shifty site (U UUC AUA) that responds strongly to a isoleucine‐tRNA limitation. Our findings are as follows: (i) the downstream stem–loop has little effect on frameshifting in growing, unstarved cells; (ii) the stem–loop increases the frameshifting effect of isoleucine‐tRNA limitation about fourfold, and this synergism is maximal with a distance of 5–9 nucleotides between the ‘hungry’ AUA codon and the stem–loop; and (iii) a stem–loop of different sequence at the same position has the same effect.