FRAMESHIFTING BY EUKARYOTIC RIBOSOMES DURING EXPRESSION OF ESCHERICHIA-COLI RELEASE FACTOR-II

Normal translation of the gene for E. coli release factor 2 (RF-2) is characterized by a + 1 frameshift event that occurs with 30-50% efficiency. Frameshifting on synthetic RF-2 mRNA by eukaryotic ribosomes has also been observed, even though they lack the capability to interact with the frameshift signal in the same manner as prokaryotic ribosomes. We have mutagenized the sequence of the RF-2 gene to eliminate the need for a frameshift, thereby allowing frameshifting efficiency to be measured by direct comparison of RF-2 production from the mutant with production from the wild-type. Measurements using this approach confirm that frameshifting by rabbit reticulocyte lysate ribosomes occurs at the frameshift region, but with a limited efficiency of approximately 0.4%.