Mitochondrial research provides new insights into how our cells process RNA for energy production

Molecular reconstruction of the human mitochondrial RNase Z complex superimposed on frozen tomography sections using human cell mitochondria. Credit: Genis Valentin Gese.
Researchers at Karolinska Institutet’s Department of Cell and Molecular Biology have made a major discovery about how human cells produce energy. Their study, published in The EMBO Journal, revealed detailed mechanisms of how mitochondria process RNA (tRNA) molecules essential for energy production.
Mitochondria require properly processed tRNA to make proteins for energy. Problems with tRNA processing can lead to severe mitochondrial diseases. Until now, the exact process of tRNA maturation in mitochondria was not well understood.
“Our study reveals at the molecular level how the mitochondrial RNase Z complex recognizes and processes tRNA molecules,” said Genís Valentín Gesé, lead author of the study. “By using advanced cryo-electron microscopy, we were able to visualize the behavior of the complex and capture snapshots of tRNAs at different stages of maturation. “This is an important step forward in understanding how we generate and maintain healthy function.”
The researchers used advanced cryo-electron microscopy to visualize the mitochondrial RNase Z complex, which is important for tRNA maturation. They captured high-resolution images showing how this complex processes tRNA molecules in a step-by-step manner.
“Looking at the RNase Z complex in such detail is like looking at the finely tuned gears of an engine,” Valentín Gesé explained. “We can observe how each component interacts with tRNA, providing valuable insight into the precise mechanism of tRNA maturation.”


Credit: EMBO Journal (2024). DOI: 10.1038/s44318-024-00297-w
Clarifying the mechanism of sequential processing
One of the key discoveries was the discovery of the 5′ to 3′ processing order of tRNAs, which ensures that tRNAs are correctly prepared for protein synthesis. This study also describes how the RNase Z complex avoids cleavage of tRNAs that already have the essential 3′-CCA tail, preventing errors in tRNA processing.
“Understanding the directionality of tRNA processing is very important,” said Martin Hällberg, senior author of the study. “This ensures that the tRNA molecules mature and function properly, which is essential for mitochondria to efficiently produce energy.”
Importantly, this study links specific mutations in the ELAC2 gene to mitochondrial disease. Understanding these mutations can help develop targeted therapies for conditions such as cardiomyopathy and intellectual disability.
“Visualizing where these mutations occur and how they affect the structure and function of the RNase Z complex allows us to understand the molecular basis of specific mitochondrial diseases,” Hällberg He explains. “This knowledge is critical to developing targeted therapies that correct or compensate for these deficiencies.”
This breakthrough provides a new pathway for the diagnosis and treatment of mitochondrial diseases and improves our overall understanding of mitochondrial biology.
Further information: Genís Valentín Gesé et al, Structural basis of 3′-tRNA maturation by the human mitochondrial RNase Z complex, The EMBO Journal (2024). DOI: 10.1038/s44318-024-00297-w
Provided by Karolinska Institute
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