Putative anticodons in mitochondrial tRNA sidearm loops: Pocketknife tRNAs?

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Genomics

Background:

• The role of tRNA sidearm loops in carrying anticodons is debated, with hypotheses including crossover events or translation by tRNA halves.
• Previous research suggests potential coevolution between tRNA structures and codon usage.

Purpose of the Study:

• To investigate the hypothesis that tRNA sidearm loops bear anticodons and their translational implications.
• To explore the coevolution of tRNA sidearm loop structures with codon usage and potential tetracodon recognition.

Main Methods:

• Comparative genomic analysis of Drosophila and yeast mitochondrial genomes.
• Analysis of coevolutionary patterns between tRNA sidearm loop lengths, codon families, and antisense tRNAs.
• Examination of expanded anticodons (tetracodons) and their relationship with sidearm loop size.

Main Results:

• Coevolution observed between tRNA sidearm loop numbers and codon families in Drosophila mitochondria (macroevolution).
• Microevolutionary patterns show coevolution for single codon families across genomes, partly confounded by antisense tRNAs.
• Expanded tRNA sidearm loops correlate with tetracodon numbers, supporting translational activity of sidearm anticodons.

Conclusions:

• Findings slightly favor hypotheses involving isolated stem-loops over crossover events.
• The coevolution of tetracodons and sidearm loops strengthens translational hypotheses for tRNA sidearm anticodons.
• The study supports functional roles for tRNA sidearm anticodons, tetragenes, and antisense tRNAs in mitochondrial translation.