The human mitochondrial translation factor TACO1 alleviates mitoribosome stalling at polyproline stretches

• Published in: Nucleic acids research Vol. 52; no. 16; pp. 9710 - 9726
• Main Authors: Brischigliaro, Michele, Krüger, Annika, Moran, J Conor, Antonicka, Hana, Ahn, Ahram, Shoubridge, Eric A, Rorbach, Joanna, Barrientos, Antoni
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 09-09-2024
• Subjects: Cyclooxygenase 1; Electron Transport Complex IV - genetics; Electron Transport Complex IV - metabolism; HEK293 Cells; Humans; Medicin och hälsovetenskap; Mitochondria - genetics; Mitochondria - metabolism; Mitochondrial Proteins - genetics; Mitochondrial Proteins - metabolism; Mitochondrial Ribosomes - metabolism; Molecular Biology; Peptide Elongation Factors - genetics; Peptide Elongation Factors - metabolism; Peptide Initiation Factors - genetics; Peptide Initiation Factors - metabolism; Peptides - genetics; Peptides - metabolism; Protein Biosynthesis
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gkae645

Abstract
The prokaryotic translation elongation factor P (EF-P) and the eukaryotic/archaeal counterparts eIF5A/aIF5A are proteins that serve a crucial role in mitigating ribosomal stalling during the translation of specific sequences, notably those containing consecutive proline residues (1,2). Although mitochondrial DNA-encoded proteins synthesized by mitochondrial ribosomes also contain polyproline stretches, an EF-P/eIF5A mitochondrial counterpart remains unidentified. Here, we show that the missing factor is TACO1, a protein causative of a juvenile form of neurodegenerative Leigh's syndrome associated with cytochrome c oxidase deficiency, until now believed to be a translational activator of COX1 mRNA. By using a combination of metabolic labeling, puromycin release and mitoribosome profiling experiments, we show that TACO1 is required for the rapid synthesis of the polyproline-rich COX1 and COX3 cytochrome c oxidase subunits, while its requirement is negligible for other mitochondrial DNA-encoded proteins. In agreement with a role in translation efficiency regulation, we show that TACO1 cooperates with the N-terminal extension of the large ribosomal subunit bL27m to provide stability to the peptidyl-transferase center during elongation. This study illuminates the translation elongation dynamics within human mitochondria, a TACO1-mediated biological mechanism in place to mitigate mitoribosome stalling at polyproline stretches during protein synthesis, and the pathological implications of its malfunction.
Graphical Abstract
Graphical Abstract