Figure 3.

The effect of structure in the mRNA 5′ UTR on translation. (A) Different amounts of a capped luciferase mRNA with an unstructured 5′ UTR of length 75 nt were added to cell-free extracts from S.pombe and S.cerevisiae to titrate the activity of the translation apparatus. Incubations were for 60 min. The S.pombe extract was either from a wild type CB12 strain or from an isogenic strain bearing the kanMX6::tif452 disruption. The S.cerevisiae extract was from the dsRNA-deficient strain 1773. (B) The same titrations as in (A) were performed, except that we used a derivative of the luciferase mRNA into which the B3 stem–loop structure (24) had been inserted. (C) The luciferase activity obtained with 250 ng of the B3-containing mRNA expressed as a percentage of the activity of the unstructured mRNA at identical mRNA concentration. The x-axis indicates the type of extract, and whether recombinant eIF4E2 (200 ng) has been added to the incubation mixture. Each n-value indicates the number of times each experiment was performed.