Nuclear codon reassignments in the genomics era and mechanisms behind their evolution.
The canonical genetic code ubiquitously translates nucleotide into peptide sequence with several alterations known in viruses, bacteria, mitochondria, plastids, and single-celled eukaryotes. A new hypothesis to explain genetic code changes, termed tRNA loss driven codon reassignment, has been proposed recently when the polyphyly of the yeast codon reassignment events has been uncovered. According to this hypothesis, the driving force for genetic code changes are tRNA or translation termination factor loss-of-function mutations or loss-of-gene events. The free codon can subsequently be captured by all tRNAs that have an appropriately mutated anticodon and are efficiently charged. Thus, codon capture most likely happens by near-cognate tRNAs and tRNAs whose anticodons are not part of the recognition sites of the respective aminoacyl-tRNA-synthetases. This hypothesis comprehensively explains the CTG codon translation as alanine in Pachysolen yeast together with the long known translation of the same codon as serine in Candida albicans and related species, and can also be applied to most other known reassignments.
Group Systems Biology of Motor Proteins, Department of NMR-Based Structural Biology, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Martin
M
Kollmar
Milner Centre for Evolution, Department of Biology and Biochemistry, University of Bath, Bath, UK.
Stefanie
S
Mühlhausen
D000595:Amino Acid Sequence; D001203:Ascomycota / Q000145:classification / Q000235:genetics; D002467:Cell Nucleus / Q000235:genetics; D016798:Ciliophora / Q000166:cytology / Q000235:genetics; D003062:Codon / Q000235:genetics*; D019143:Evolution, Molecular; D005815:Genetic Code; D023281:Genomics; D008957:Models, Genetic; D010802:Phylogeny; D014176:Protein Biosynthesis; D012343:RNA, Transfer / Q000235:genetics; D013045:Species Specificity
D003062:Codon; D012343:RNA, Transfer
codon reassignment; eukaryotic evolution; genetic code; tRNA identity elements