Using mitoribosomal profiling to investigate human mitochondrial translation.

Area of Science:

• Mitochondrial Biology
• Molecular Genetics
• Ribosome Function

Background:

• Human mitochondrial gene expression exhibits unique characteristics, including the incorporation of mitochondrially-encoded tRNAs into the large mitoribosomal subunit.
• While porcine mitoribosomes use mt-tRNA^Phe, human mitoribosomes incorporate mt-tRNA^Val.
• Previous work showed that a mutation in human mt-tRNA^Val leads to preferential recruitment of mt-tRNA^Phe.

Purpose of the Study:

• To investigate the impact of altered mitoribosome composition on intra-organellar protein synthesis.
• To analyze mitoribosome behavior on mitochondrial messenger RNA (mt-mRNA) under normal and aberrant conditions.

Main Methods:

• Mitoribosomal profiling was employed to study mitoribosome dynamics on mt-mRNA.
• Analysis was conducted under both control conditions and in a cell line with aberrant mt-tRNA^Phe incorporation.

Main Results:

• Mitoribosome occupancy on transcripts was not significantly affected by non-canonical wobble base pairs at the third codon position.
• Impaired translation in the mutant mt-tRNA^Val cell line was not due to stalling on specific amino acid-encoding triplets.
• Alterations in mitoribosome-start codon interactions were not directly linked to non-cognate initiation codons or leader sequences, except in specific bicistronic RNAs.

Conclusions:

• Mitoribosomal profiling is a powerful tool for understanding mammalian mitochondrial protein synthesis.
• Integration of mt-tRNA^Phe into human mitoribosomes, despite its preference in porcine systems, results in a suboptimal structure.
• This suboptimal structure alters the interaction between human mitoribosomes and mt-mRNAs, impacting protein synthesis.