Translation-Promoting Effects of RNA Template Overhangs in the Absence of Ribosomes.

Translation requires a complex set of biomacromolecules. How it evolved is an unsolved problem. Ribosome-free, single-nucleotide translation via coupling of 3'-aminoacylated RNA to 5'-phosphoramidate-linked RNAs was shown for very short peptides. It was unclear how this process could be induced at a specific locus, regulated, and expanded. Here we show that a triplex-forming template overhang accelerates ribosome-free translation and increases its yield. An NMR-monitored model study suggested that mixed anhydrides between carboxylates of amino acid residues and phosphates can contribute to efficient peptide coupling, strengthening proximity effects. Folding into triplexes at pH 6 enhances the template effect, and unfolding at pH 8 suppresses it, suggesting a simple way of achieving "inducible translation" in a system devoid of biomacromolecules. Under mild acidic conditions, doubly RNA-linked peptides up to octamers were formed in near-quantitative yield. Taken together, our data suggests that the growth of template strands not only allows for encoding more genetic information, but may also enhance translational fitness.