FIG. 4.

In vitro frameshifting assay with yeast cell extracts. (A) The capped and polyadenylated in vitro-synthesized transcripts, used for in vitro translation reactions, shown contain the luciferase protein coding region either lacking (0-frame control [LUC0]) or containing (LUC-1) a −1 ribosomal frameshift (RFS) site. (B) Equal amounts (20 ng) of RNA were added to the in vitro translation system with an individual cell extract. The level of protein expression was measured by a luciferase assay, and the efficiency of −1 frameshifting was determined by the ratio of luciferase activity from LUC-1 to that from LUC0. The values shown are averages of at least three independent experiments done in triplicate. WT, wild type.