[Translation Termination Factor of ERFI of the Ciliate Blepharisma Japonicum Recognizes All Three Stop Codons]

We have determined the type of stop codon specificity of Blepharisma japonicum translation termination factor eRF1 in an in vitro reconstituted eukaryotic translation system and in in vivo assay (the dual reporter system). We have shown that B. japonicum eRF1 retained specificity towards all three stop codons although efficiency of peptydyl-tRNA hydrolysis in the presence of UGA is reduced in an in vitro assay. We suggest that since the heterotrich B. japonicum represents the earliest diverged lineage on phylogenetic tree of ciliates, B. japonicum has the universal genetic code as ancestor group for all ciliates.