tRNA Creation by Hairpin Duplication

Abstract

Many studies have suggested that the modern cloverleaf structure of tRNA may have arisen through duplication of a primordial hairpin, but the timing of this duplication event has been unclear. Here we measure the level of sequence identity between the two halves of each of a large sample of tRNAs and compare this level to that of chimeric tRNAs constructed either within or between groups defined by phylogeny and/or specificity. We find that actual tRNAs have significantly more matches between the two halves than do random sequences that can form the tRNA structure, but there is no difference in the average level of matching between the two halves of an individual tRNA and the average level of matching between the two halves of the chimeric tRNAs in any of the sets we constructed. These results support the hypothesis that the modern tRNA cloverleaf arose from a single hairpin duplication prior to the divergence of modern tRNA specificities and the three domains of life.

Origins and evolution of modern biochemistry: insights from genomes and molecular structure

“…This observation suggests that functional diversification in tRNA developed once the cloverleaf structure was fully formed. This is consistent with the recent proposal that structural diversification preceded the establishment of amino acid and anticodon specificities and the diversified organismal world (147). Interestingly, some few tRNA Ser , tRNA Leu , and tRNA Tyr lacked the long variable arm and were derived, suggesting the existence of take-overs in evolution that involved the loss of these substructures.…”

The evolution of the genetic code: Impasses and challenges

“…Bernhardt and co-workers (Bernhardt and Patrick, 2014;Bernhardt and Tate, 2008) have also proposed glycine as the first amino acid to enter the code. They argue that tRNA of Gly can be derived from a duplication of hairpins with CCA 3' terminus (Widman et al, 2005). Present day tRNAs have CCA at its acceptor stem, of which a part could be the origin of the NCC anticodon of tRNA Gly .…”

Extensive tRNA Gene Changes in Synthetic Brassica napus

“…This may support the idea that tRNA gene diversification preceded the divergence of species through all tRNA sequences analysis (Sun and Caetano-Anolles 2008b). tRNA and organisms did not co-evolve, and tRNA was created from a single hairpin duplication (Widmann et al 2005). It is commonly accepted that initially the acceptor stem sequences only attached a few amino acid sequences, and not all 20 amino acids were encoded ( To sum up, extensive tRNA gene alternations were induced in the early stages of allopolyploidization.…”