bims-mitran 2025-07-06 papers

Issue of 2025–07–06
four papers selected by
Andreas Kohler, Umeå University

Elife. 2025 Jun 30. pii: RP104461. [Epub ahead of print]14

Tissue-specific responses to TFAM and mtDNA copy number manipulation in prematurely ageing mice.

Laura Sophie Kremer, Guanbin Gao, Giovanni Rigoni, Roberta Filograna, Mara Mennuni, Rolf Wibom, Ákos Végvári, Camilla Koolmeister, Nils-Göran Larsson.

Somatic mitochondrial DNA (mtDNA) mutations are implicated as important drivers of ageing and age-related diseases. Their pathological effect can be counteracted by increasing the absolute amount of wild-type mtDNA via moderately upregulating TFAM, a protein important for mtDNA packaging and expression. However, strong TFAM overexpression can also have detrimental effects as it results in mtDNA hypercompaction and subsequent impairment of mtDNA gene expression. Here, we have experimentally addressed the propensity of moderate TFAM modulation to improve the premature ageing phenotypes of mtDNA mutator mice, carrying random mtDNA mutations. Surprisingly, we detect tissue-specific endogenous compensatory mechanisms acting in mtDNA mutator mice, which largely affect the outcome of TFAM modulation. Accordingly, moderate overexpression of TFAM can have negative and beneficial effects in different tissues of mtDNA mutator mice. We see a similar behavior for TFAM reduction, which improves brown adipocyte tissue homeostasis, while other tissues are unaffected. Our findings highlight that the regulation of mtDNA copy number and gene expression is complex and causes tissue-specific effects that should be considered when modulating TFAM levels. Additionally, we suggest that TFAM is not the sole determinant of mtDNA copy number in situations where oxidative phosphorylation (OXPHOS) is compromised, but other important players must be involved.

Keywords: biochemistry; chemical biology; genetics; genomics; mitochondrial DNA; mouse; mtDNA copy number; mtDNA mutations; tissue specificity

DOI: https://doi.org/10.7554/eLife.104461

Nat Commun. 2025 Jul 01. 16(1): 5435

Selfish mutations promote age-associated erosion of mtDNA integrity in mammals.

Ekaterina Korotkevich, Daniel N Conrad, Zev J Gartner, Patrick H O'Farrell.

Mutations in mitochondrial DNA (mtDNA) accumulate during aging and contribute to age-related conditions. High mtDNA copy number masks newly emerged recessive mutations; however, phenotypes develop when cellular levels of a mutant mtDNA rise above a critical threshold. The process driving this increase is unknown. Single-cell DNA sequencing of mouse and human hepatocytes detected increases in abundance of mutant alleles in sequences governing mtDNA replication. These alleles provided a replication advantage (drive) leading to accumulation of the affected genome along with a wide variety of associated passenger mutations, some of which are detrimental. The most prevalent human mtDNA disease variant, the 3243A>G allele, behaved as a driver, suggesting that drive underlies prevalence. We conclude that replicative drive amplifies linked mtDNA mutations to a threshold at which phenotypes are seen thereby promoting age-associated erosion of the mtDNA and influencing the transmission and progression of mitochondrial diseases.

DOI: https://doi.org/10.1038/s41467-025-60477-y

Nat Commun. 2025 Jul 02. 16(1): 6083

Immuno-metabolic stress responses control longevity from mitochondrial translation inhibition in C. elegans.

Iman Man Hu, Marte Molenaars, Yorrick R J Jaspers, Bauke V Schomakers, Michel van Weeghel, Amber Bakker, Melanie Modder, Joseph P Dewulf, Guido T Bommer, Arwen W Gao, Georges E Janssens, Riekelt H Houtkooper.

Perturbing mitochondrial translation represents a conserved longevity intervention, with proteostasis processes proposed to mediate the resulting lifespan extension. Here, we explore whether other mechanisms may contribute to lifespan extension upon mitochondrial translation inhibition. Using multi-omics and functional in vivo screening, we identify the ethylmalonyl-CoA decarboxylase orthologue C32E8.9 in C. elegans as an essential factor for longevity induced by mitochondrial translation inhibition. Reducing C32E8.9 completely abolishes lifespan extension from mitochondrial translation inhibition, while mitochondrial unfolded protein response activation remains unaffected. We show that C32E8.9 mediates immune responses and lipid remodeling, which play crucial roles in the observed lifespan extension. Mechanistically, sma-4 (a TGF-β co-transcription factor) serves as an effector of C32E8.9, responsible for the immune response triggered by mitochondrial translation inhibition. Collectively, these findings underline the importance of the "immuno-metabolic stress responses" in longevity upon mitochondrial translation inhibition and identify C32E8.9 as a central factor orchestrating these responses.

DOI: https://doi.org/10.1038/s41467-025-61433-6

Nat Commun. 2025 Jul 01. 16(1): 5792

Mechanism of nascent chain removal by the ribosome-associated quality control complex.

Wenyan Li, Talia Scheel, Peter S Shen.

Errors during translation can cause ribosome stalling, leaving incomplete nascent chains attached to large ribosomal subunits. Cells rely on the Ribosome-associated Quality Control (RQC) complex to recognize, process, and remove these aberrant proteins to maintain proteostasis. Despite its importance, the mechanisms by which the RQC orchestrates nascent chain processing and extraction have remained unclear. Here, we present a cryo-EM structure of the RQC complex from budding yeast, revealing how its core components function in nascent chain removal. We show that the Cdc48 ATPase and its Ufd1-Npl4 adaptor are recruited by the Ltn1 E3 ubiquitin ligase to extract ubiquitylated peptides from the 60S ribosome. Additionally, we find that Rqc1 bridges the 60S subunit with ubiquitin and Ltn1, facilitating formation of K48-linked polyubiquitin chains. These findings provide a structural and mechanistic framework for understanding how the RQC complex collaborates to clear stalled translation products, advancing insight into cellular protein quality control.

DOI: https://doi.org/10.1038/s41467-025-61235-w