Comparison of Two Possible Evolutionary Mechanisms of the 62 tRNA Codon Sequences

Fangping Wei,Bourong Liu,Zhenxiong Lan,Luming Shen,Yu Xue

doi:10.4236/jbise.2017.104014

Abstract

The tRNAs were divided into 62 groups based on the codons they carried and networks were constructed. Phylogenetic trees were constructed in parallel and antiparallel directions based on the parameters of these networks. Point mutations were found in the codon sites in the same clusters in the entire parallel and antiparallel phylogenetic trees, whereas there was no evidence of a complementary duplication mechanism in the corresponding antiparallel phylogenetic trees. The codons of isoaccepting tRNAs were found in neighboring clusters or distributed within a very small distance so the codons with only one base difference remained very close, which was perfectly consistent with the hypothesis that a new tRNA gene could be recruited from an isoaccepting group via another point mutation.

Highlights

There are many reports on mitochondrial tRNA mutations would linked with inherited diseases [1] [2] [3], i.e., mutations in tRNAIle, tRNALys and tRNASer(UCN) are known to cause different mt encephalomyopathies or non-syndromic deafness [3]
Point mutations were found in the codon sites in the same clusters in the entire parallel and antiparallel phylogenetic trees, whereas there was no evidence of a complementary duplication mechanism in the corresponding antiparallel phylogenetic trees
We found that some codons of the isoaccepting tRNAs appeared in the same cluster and neighboring clusters

Summary

Introduction

There are many reports on mitochondrial (mt) tRNA mutations would linked with inherited diseases [1] [2] [3], i.e., mutations in tRNAIle, tRNALys and tRNASer(UCN) are known to cause different mt encephalomyopathies or non-syndromic deafness [3]. The mutation of tRNA genes has a research hotspot. Many tRNA sequences have been found and deposited in a database [4] and they all conform to one of 62 codon sequence groups (two codon groups are absent from the database, i.e., aaa and cta). All modern tRNA sequences have evolved from a common ancestor, but their evolutionary mechanism remains an open question. Two possible mechanisms have been proposed to explain the origin and evolution of modern tRNAs, i.e., “point mutation” and “template duplication” [5].

Methods

Results

Conclusion