A translational frameshift is necessary in the synthesis of Escherichia coli 
release factor 2 (RF-2) to bypass an in-frame termination codon within the 
coding sequence. The nucleotide sequence preceding the in-phase stop codon 
within RF-2 mRNA is complementary to the 3' anti-(Shine-Dalgarno sequence) 
region found in prokaryotic 16S rRNA and Weiss et al. (1988) have concluded that 
this pairing triggers the frameshift event. In vitro production of RNA coding 
for RF-2, suitable for translation on eukaryotic ribosomes, has enabled testing 
of whether eukaryotic ribosomes can frameshift at this sequence. The 18S rRNA of 
eukaryotic ribosomes does not contain the 3' anti-(Shine-Dalgarno sequence) 
region. The prokaryotic RF-2 gene and the gene for the other release factor, 
RF-1, which does not contain an in-frame stop codon, were subcloned into 
transcription vectors such that the RNA transcripts produced in vitro would 
resemble a typical eukaryotic mRNA. These RF-1 and RF-2 RNAs both synthesized a 
major product of Mr approximately 45,000 when translated in vitro within 
reticulocyte lysate; the size expected for full length RF-1 and RF-2 molecules. 
The RF-2 product was immunoprecipitated by RF-2-specific antibodies, including 
those to regions of the protein encoded in the mRNA downstream from the 
frameshift site. The putative premature termination product, an oligopeptide of 
25 amino acids, was not detected, but a chemically synthesized derivative was 
shown to be very unstable within the translation system. Although it was not 
possible therefore to calculate an absolute efficiency of frameshifting, the 
relative efficiency of the translation of RF-2 RNA was estimated to be 10-20% of 
that of RF-1 RNA in the reticulocyte system. This was similar to the relative 
synthesis of the two proteins in a plasmid-DNA-directed prokaryotic 
transcription/translation system. These results show that in vitro on eukaryotic 
ribosomes where the Shine-Dalgarno-type interaction is not possible, high 
efficiency frameshifting around the in-phase stop codon in the RF-2 mRNA can 
still occur.