bims-mirnam Biomed News
on Mitochondrial RNA metabolism
Issue of 2026–07–19
seven papers selected by
Hana Antonicka, McGill University



  1. Trends Biochem Sci. 2026 Jul 15. pii: S0968-0004(26)00204-5. [Epub ahead of print]
      Mitochondrial tRNAs (mt-tRNAs) are central to energy production by translating essential oxidative phosphorylation subunits. Following transcription, mt-tRNAs undergo diverse processing steps, post-transcriptional modifications, and aminoacylation, which are critical for their functions. In this article, we review how human mt-tRNA-modifying enzymes deposit various post-transcriptional modifications onto mt-tRNAs, encompassing both well-characterized and less-understood marks. We also summarize the principles, peculiarities, and critical roles of mt-tRNA charging and proofreading, and highlight recently uncovered noncanonical functions of mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs). Collectively, these recent findings demonstrate the dynamic regulatory mechanisms of mt-tRNA modification and aminoacylation, the extensive involvement of mt-aaRSs in cellular metabolic pathways, and the promising potential of targeting these enzymes in therapeutics.
    Keywords:  editing; mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs); mitochondrial diseases; mitochondrial translation; noncanonical functions; post-transcriptional modification
    DOI:  https://doi.org/10.1016/j.tibs.2026.06.009
  2. Int J Mol Sci. 2026 Jun 29. pii: 5858. [Epub ahead of print]27(13):
      More than 160 types of post-transcriptional RNA modifications have been identified, revealing considerable diversity in their types, abundances, distributions, and functional roles across different RNAs, cells, and tissues in humans. Recent advances in high-throughput sequencing technologies have enabled the systematic detection of dynamic RNA modifications, including N6-methyladenosine (m6A) and inosine (I). In this review, we focus on RNA modifications in eukaryotic mRNA and provide an overview of current high-throughput methodologies for detecting the most abundant adenosine-related modifications, including m6A and adenosine-to-inosine (A-to-I) RNA editing. Finally, we discuss the major challenges that remain in the field and highlight key directions for future research.
    Keywords:  Illumina; RNA editing; RNA modifications; direct RNA sequencing; epitranscriptomics; long-read sequencing; m6A
    DOI:  https://doi.org/10.3390/ijms27135858
  3. J Med Chem. 2026 Jul 13.
      Leucine-rich pentatricopeptide repeat containing (LRPPRC), a critical regulator of mitochondrial gene expression, is overexpressed in various malignancies and sustains oxidative phosphorylation (OXPHOS)-dependent adenosine triphosphate (ATP) production essential for tumor growth, chemoresistance, and stem cell survival, rendering it a promising therapeutic target. Herein, using an aptamer-assisted fluorescence polarization platform, we identified acylhydrazone-skeleton inhibitors targeting LRPPRC's RNA-binding domain, leading to the design and synthesis of over 60 derivatives. Lead compound 3o exhibited excellent LRPPRC inhibitory activity (92% at 6.25 μM vs 38% for gossypol acetate (GAA)) and induced robust LRPPRC degradation. Notably, 3o downregulated downstream OXPHOS subunits and ATP synthase, eliciting broad antiproliferative effects, particularly in refractory and drug-resistant A549, BXPC-3, and NCI-H1975 cells (IC50 = 0.54, 0.27, and 1.39 μM, respectively). In PC9 and HCT116 xenografts, 3o achieved tumor growth inhibition (TGI) rates of 73 and 49% with favorable safety profiles. Overall, we developed novel biphenyl-acylhydrazone LRPPRC inhibitors as potent antitumor agents acting via OXPHOS modulation, providing a valuable lead compound for cancer therapy.
    DOI:  https://doi.org/10.1021/acs.jmedchem.6c00936
  4. bioRxiv. 2026 Jul 09. pii: 2026.07.08.737379. [Epub ahead of print]
      RNA surveillance pathways maintain transcriptome integrity by eliminating aberrant, excess, and non-functional RNAs, yet it remains unclear whether distinct tissues exhibit equivalent requirements for RNA quality control. Here, we investigated the tissue-specific consequences of impaired RNA surveillance using a Drosophila allelic series of the RNA exosome subunit Rrp40. Comparative transcriptomic analyses revealed that neuronal-enriched head tissue and muscle-enriched thorax tissue exhibit largely distinct molecular programs following reduced RNA exosome activity despite disruption of the same RNA surveillance machinery. Antisense RNAs emerged as particularly sensitive targets of RNA exosome dysfunction, accumulating preferentially in neuronal tissue and largely independent of changes in overlapping sense host transcripts, indicating enhanced requirements for RNA-level quality control within the nervous system. Although tissue-specific transcriptomic alterations diverged substantially, multiple analyses converged on mitochondrial homeostasis as a shared vulnerability. Reduced RNA exosome activity was associated with widespread dysregulation of nuclear-encoded mitochondrial genes, mitochondrial dynamics pathways, and mitochondrial RNA regulatory programs, accompanied by progressive defects in mitochondrial organization, membrane potential, and ATP production. Mitochondrial dysfunction was further associated with activation of proteostatic stress pathways, including p62 accumulation and increased ubiquitination. Together, these findings demonstrate that tissue context shapes the molecular consequences of impaired RNA surveillance while revealing mitochondrial homeostasis as a convergent vulnerability arising from transcriptome instability. More broadly, our findings suggest that distinct tissue-specific defects in RNA regulation converge on common cellular vulnerabilities that ultimately govern tissue homeostasis.
    DOI:  https://doi.org/10.64898/2026.07.08.737379
  5. bioRxiv. 2026 Jul 08. pii: 2026.07.06.731365. [Epub ahead of print]
    ENCODE Project Consortium
      We present the Encyclopedia of DNA Elements (ENCODE), a reference map of the genomic basis of gene regulation. A product of more than two decades of systematic interrogation of genome function, ENCODE encompasses more than 16,000 genome-wide experiments, predominantly in primary cells and tissues, focused on three core layers of genome function. First, ENCODE now provides a catalog of gene regulatory elements. The catalog is based on a foundation of 5.3 million DNase I hypersensitive sites that delineate essentially all chromatin-accessible regulatory DNA in the human genome, as well as extensive maps of chromatin states, transcription factor occupancy, and nascent transcription, and systematic predictions of the functional consequences of non-coding genetic variants on regulatory element activity. Second, ENCODE expands the catalog of genes and transcripts, which now includes nearly 18,000 novel human long noncoding RNA genes, nearly 150,000 novel transcript isoforms, and genome-wide maps of transcript stability across cell types and time. Third, ENCODE now maps physical and functional interactions among regulatory elements and genes across more than 100 human tissues and cell lines at up to 10 bp resolution. Those studies reveal a vast network of interactions among millions of loop anchors across and links those interactions to gene expression. Through parallel studies in mice, ENCODE also provides extensive maps of gene regulatory elements, transcripts, and their interactions across the mouse postnatal development. Together, the Encyclopedia of DNA Elements provides a foundational framework for genome-focused studies of human and mouse biology.
    DOI:  https://doi.org/10.64898/2026.07.06.731365
  6. Cell Death Differ. 2026 Jul 15.
      Colorectal cancer stem cells (CSCs) drive tumor progression through poorly understood metabolic-epigenetic crosstalk. Here, we identify mitochondrial RNA polymerase POLRMT as a key link connecting mitochondrial transcription to CSC maintenance. Clinically, POLRMT is overexpressed in colorectal cancer (CRC) tissues and correlates with poor prognosis. Genetic ablation or pharmacological inhibition of POLRMT suppresses CSC self-renewal and tumorigenicity across cell line-derived CSCs, CRC organoids, and xenograft models. Mechanistically, POLRMT deficiency triggers mitochondrial dysfunction, which unexpectedly elevates the demethylase KDM6B expression, α-ketoglutarate (α-KG) levels, and Dickkopf-1 (DKK1) expression, thereby transcriptionally silencing Wnt/β-catenin signaling and collapsing the CSC niche. Restoration of β-catenin rescues tumorigenicity in POLRMT-knockout (KO) cells, confirming the hierarchy of this signaling cascade. Crucially, POLRMT catalytic activity and mitochondrial localization are indispensable for sustaining this axis. Our work unveils POLRMT as a metabolic gatekeeper that licenses CSC plasticity through KDM6B-α-KG/H3K27me3-mediated chromatin remodeling, proposing the mitochondrial transcription machinery as a therapeutic target for dismantling the CSC hierarchy in CRC.
    DOI:  https://doi.org/10.1038/s41418-026-01807-5
  7. J Cardiovasc Transl Res. 2026 Jul 13. pii: 90. [Epub ahead of print]19(1):
      Heart failure (HF) is closely linked to mitochondrial dysfunction, featured by abnormal energy metabolism, excessive reactive oxygen species (ROS), and imbalanced mitochondrial dynamics. Clinically, effective targeted therapies for mitochondrial dysfunction are still lacking, which aggravates HF and multi-organ injury. Mitochondrial non-coding RNAs (mt-ncRNAs) form a regulatory network critical for mitochondrial function. Among them, mitochondrial-encoded circular RNAs (mecciRNAs) and mitochondrial double-stranded RNAs (mt-dsRNAs) are research hotspots. mecciRNAs protect the heart by assisting protein import and regulating mitochondrial pores and ROS; their degradation worsens HF, while exogenous supplementation alleviates injury. mt-dsRNAs arise from aberrant mitochondrial transcription and contribute to myocardial injury and remodeling via MAVS, cGAS-STING, and PNPT1 pathways. Gene therapy targeting mecciRNAs and mt-dsRNAs combined with mitochondrial delivery represents a promising strategy for HF treatment.
    Keywords:  Heart failure; Mitochondrial genome; Mitochondrial-penetrating peptides; Mt-dsRNA; Mt-mitochondrial-encoded circular RNAs
    DOI:  https://doi.org/10.1007/s12265-026-10809-0