Translation termination in Arabidopsis thaliana: characterisation of three versions of release factor 1

Translation termination is mediated in all eukaryotes by the two release factors eRF1 and eRF3. Most organisms have a single eRF1 gene, however, three isogenes of eRF1 are found in Arabidopsis thaliana. They have no introns in the coding region which may indicate that some are pseudogenes. However, each was expressed and able to rescue a temperature sensitive eRF1-mutant of Saccharomyces cerevisiae indicating functional redundancy in A. thaliana. While normally a highly accurate process, translation termination can be directed to fail by sequence elements within an messenger RNA (mRNA). Interestingly, a well-characterised readthrough element follows the stop codon in one of these three isogenes (designated eRF1-1). This element was shown to be capable of inducing readthrough in an in vitro assay using a dual luciferase reporter, but surprisingly readthrough could not be detected using the complete gene context. The results highlight the diversity and duplication of genes within plant genomes, but also emphasize the conservation of the translation process across kingdoms.