bims-tricox 2024-12-22 papers

Issue of 2024–12–22
two papers selected by
Yash Verma, University of Zurich

J Biol Chem. 2024 Dec 13. pii: S0021-9258(24)02589-4. [Epub ahead of print] 108087

Crucial role and conservation of the three [2Fe-2S] clusters in the human mitochondrial ribosome.

Linda Boß, Oliver Stehling, Hans-Peter Elsässer, Roland Lill.

Mitochondria synthesize only a small set of their proteins on endogenous mitoribosomes. These particles differ in structure and composition from both their bacterial 70S ancestors and cytosolic 80S ribosomes. Recently published high resolution structures of the human mitoribosome revealed the presence of three [2Fe-2S] clusters in the small and large subunits. Each of these clusters is coordinated in a bridging fashion by cysteine residues from two different mitoribosomal proteins. Here, we investigated the cell biological and biochemical roles of all three Fe/S clusters in mitochondrial function and assembly. First, we found a requirement of both early and late factors of the mitochondrial iron-sulfur cluster assembly machinery for protein translation indicating that not only the mitoribosome [2Fe-2S] clusters but also the [4Fe-4S] cluster of the mitoribosome assembly factor METTL17 are required for mitochondrial translation. Second, siRNA-mediated depletion of the cluster-coordinating ribosomal proteins bS18m, mS25 or mL66 and complementation with either the respective wild-type or cysteine-exchange proteins unveiled the importance of the clusters for assembly, stability, and function of the human mitoribosome. As a consequence, the lack of cluster binding to mitoribosomes impaired the activity of the mitochondrial respiratory chain complexes and led to altered mitochondrial morphology with a loss of cristae membranes. Finally, in silico investigation of the phylogenetic distribution of the cluster-coordinating cysteine motifs indicated their presence in most metazoan mitoribosomes, with exception of ray-finned fish. Collectively, our study highlights the functional need of mitochondrial Fe/S protein biogenesis for both protein translation and respiratory energy supply in most metazoan mitochondria.

Keywords: Protein synthesis; biogenesis; iron-sulfur protein assembly; mitochondria; mitochondrial respiratory chain; ribosome assembly

DOI: https://doi.org/10.1016/j.jbc.2024.108087

J Cell Biol. 2025 Feb 03. pii: e202409050. [Epub ahead of print]224(2):

A proteome-wide yeast degron collection for the dynamic study of protein function.

Rosario Valenti, Yotam David, Dunya Edilbi, Benjamin Dubreuil, Angela Boshnakovska, Yeynit Asraf, Tomer-Meir Salame, Ehud Sass, Peter Rehling, Maya Schuldiner.

Genome-wide collections of yeast strains, known as libraries, revolutionized the way systematic studies are carried out. Specifically, libraries that involve a cellular perturbation, such as the deletion collection, have facilitated key biological discoveries. However, short-term rewiring and long-term accumulation of suppressor mutations often obscure the functional consequences of such perturbations. We present the AID library which supplies "on demand" protein depletion to overcome these limitations. Here, each protein is tagged with a green fluorescent protein (GFP) and an auxin-inducible degron (AID), enabling rapid protein depletion that can be quantified systematically using the GFP element. We characterized the degradation response of all strains and demonstrated its utility by revisiting seminal yeast screens for genes involved in cell cycle progression as well as mitochondrial distribution and morphology. In addition to recapitulating known phenotypes, we also uncovered proteins with previously unrecognized roles in these central processes. Hence, our tool expands our knowledge of cellular biology and physiology by enabling access to phenotypes that are central to cellular physiology and therefore rapidly equilibrated.

DOI: https://doi.org/10.1083/jcb.202409050