Dataset Information

Distinct roles for human mtIF2 and mtIF3 in non-canonical mitochondrial translation.

ABSTRACT: The synthesis of mitochondrial OXPHOS complexes is central to cellular metabolism, yet many molecular details of mitochondrial translation remain elusive. It is commonly held view that translation initiation in human mitochondria proceeded in a manner similar to bacterial systems, with the mitoribosomal small subunit bound to the initiation factors, mtIF2 and mtIF3, along with initiator tRNA and an mRNA. However, unlike in bacteria, most human mitochondrial mRNAs lack 5′ leader sequences that can mediate small subunit binding, raising the question of how leaderless mRNAs are recognized by mitoribosomes. By using novel in vitro mitochondrial translation initiation assays, alongside biochemical and genetic characterization of cellular knockouts of mitochondrial translation factors, we describe unique features of translation initiation in human mitochondria. We show that in vitro, leaderless mRNA transcripts can be loaded directly onto assembled 55S mitoribosomes, but not onto the mitoribosomal small subunit (28S). In addition, we demonstrate that while mtIF2 is indispensable for mitochondrial translation, mtIF3 activity is not required for translation of leaderless mitochondrial transcripts but is essential for translation of ATP6 in the case of the bicistronic ATP8/ATP6 transcript. Our results confirm important evolutionary divergences of the mitochondrial translation system, and further our understanding of a process central to eukaryotic metabolism.

ORGANISM(S): Homo sapiens

PROVIDER: GSE156937 | GEO | 2022/12/01

REPOSITORIES: GEO

ACCESS DATA

Dataset's files

Source:

			Action	DRS
		Other

Items per page:

1 - 1 of 1

Similar Datasets

Project description:Mitochondrial ribosomes (mitoribosomes) have undergone substantial structural remodelling throughout evolution leading to distinct structural properties compared to their prokaryotic ancestors. Compared to their prokaryotic counterparts, mitoribosomes show a substantial loss of ribosomal RNA (rRNA), whilst acquiring unique mitochondrial proteins located on the periphery of the mitoribosome. This extended protein content suggests mitochondrial-specific functions of these proteins involved in mitochondrial mRNA selective-translation activation, ribosome assembly, translation regulation rather than exclusively structural scaffolding. We investigated the functional properties of the 14 unique (mitochondria-specific or supernumerary) mammalian mitoribosomal proteins (snMRP) in the small mitochondrial subunit (mtSSU) by CRISPR-mediated knockout and describe their specific effect on mitoribosome integrity and function. Unexpectedly, we show that each snMRP knockout leads to a unique pattern of mitoribosome instability with variable effects on mitochondrial protein synthesis as essential structural components and all – with the exception of mS37 (MRPS37, CHCHD1) – to almost complete loss of protein synthesis. Concomitantly, through steady-state proteomic analysis we confirm a modular assembly of the mtSSU. Surprisingly, mS37 was found to have impaired stability in all our tested mtSSU and large mitochondrial subunit (mtLSU) snMRPs knockouts as well as in patient-derived cell lines, suggesting an extended role of the protein in mtSSU pre-translation initiation steps. As mitochondrial intermembrane (IMS) targeted protein – a eukaryotic-confined localisation mechanism – with additional unique MIA40 (CHCHD4)-oxidisable motifs involved in the disulfide relay system, mS37 could have a specific role in mitochondrial translation regulation. Indeed, we find oxidation of the cysteines in the CX9C motif of mS37 to be essential for its stability, confirming mS37 regulating mitochondrial translation regulation.

Dataset Information

Distinct roles for human mtIF2 and mtIF3 in non-canonical mitochondrial translation.

Dataset's files

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets