Chimeric Translation for Mitochondrial Peptides: Regular and Expanded Codons

Area of Science:

• Molecular Biology
• Genetics
• Proteomics

Background:

• Frameshifting protein translation occurs via tRNA anticodon expansions, leading to amino acid insertions.
• Previous studies analyzed human mitochondrial proteomic data, detecting peptides solely from expanded codon translation.

Purpose of the Study:

• Reanalyze human mitochondrial proteomic data to identify chimeric peptides with both regular and expanded codon translations.
• Investigate the role of frameshifting in generating protein diversity within the mitochondrial genome.

Main Methods:

• Reanalyzed existing human mitochondrial MS proteomic datasets (Fisher and Waters technologies).
• Searched for peptides containing at least eight consecutive amino acids from regular tricodons and eight adjacent from expanded codons.
• Identified chimeric peptides resulting from mono- and dinucleotide expansions.

Main Results:

• Detected 42 chimeric peptides with mononucleotide expansions and 37 with dinucleotide expansions.
• Identified standard human mitochondrial proteins within the regular tricodon-translated portions of chimeric peptides.
• Confirmed the co-occurrence of regular and expanded codon translation in adjacent peptide segments.

Conclusions:

• Chimeric translation significantly increases the diversity of mitogenome-encoded proteins, potentially yielding novel functional proteins.
• This phenomenon may arise from tRNAs with expanded anticodons or RNA editing processes.
• Findings support statistical translation producing alternative protein variants and highlight the need to consider unintended products in genetic engineering.