Capped mRNA with a single nucleotide leader is optimally translated in a primitive eukaryote, Giardia lamblia.

摘要: The 5'-untranslated region (5'-UTR) of an mRNA plays important role in translation initiation eukaryotes. A minimal length about 20 nucleotides is required to prevent leaky ribosome scanning. In one the most primitive eukaryotes, Giardia lamblia, however, mRNAs have 5'-UTRs mostly range 0 14 without a conserved sequence, which raises question on how could effectively scan such short for accurate translation. present study, we expressed capped transcripts luciferase gene trophozoites via transfection and observed that when 5'-UTR transcript was lengthened from 9 21 nucleotides, there corresponding decrease efficiency. Conversely, shortening nine down single nucleotide did not result any reduced or Translation appeared initiate exclusively first codon located downstream cap. Experimental evidence indicated also stem-loop structure immediately exerted significant inhibition consisted less than seven nucleotides. This inhibitory effect abolished by increasing distance between cap-G either upstream start codon, thus suggesting spatial requirement effective recruitment. Overall, our results suggest absence scanning AUG initiating Giardia. with leader apparently sufficient recruiting