bims-tricox 2025-06-29 papers

Issue of 2025–06–29
three papers selected by
Yash Verma, University of Zurich

Nat Commun. 2025 Jun 25. 16(1): 5388

The mitochondrial methylation potential gates mitoribosome assembly.

Ruth I C Glasgow, Vivek Singh, Lucía Peña-Pérez, Alissa Wilhalm, Marco F Moedas, David Moore, Florian A Rosenberger, Xinping Li, Ilian Atanassov, Mira Saba, Miriam Cipullo, Joanna Rorbach, Anna Wedell, Christoph Freyer, Alexey Amunts, Anna Wredenberg.

S-adenosylmethionine (SAM) is the principal methyl donor in cells and is essential for mitochondrial gene expression, influencing RNA modifications, translation, and ribosome biogenesis. Using direct long-read RNA sequencing in mouse tissues and embryonic fibroblasts, we show that processing of the mitochondrial ribosomal gene cluster fails in the absence of mitochondrial SAM, leading to an accumulation of unprocessed precursors. Proteomic analysis of ribosome fractions revealed these precursors associated with processing and assembly factors, indicating stalled biogenesis. Structural analysis by cryo-electron microscopy demonstrated that SAM-dependent methylation is required for peptidyl transferase centre formation during mitoribosome assembly. Our findings identify a critical role for SAM in coordinating mitoribosomal RNA processing and large subunit maturation, linking cellular methylation potential to mitochondrial translation capacity.

DOI: https://doi.org/10.1038/s41467-025-60977-x

Protoplasma. 2025 Jun 24.

Tric proteins and TOM complex subunits are involved in the import of short DNA fragments into Arabidopsis mitochondria.

Tarasenko T A, Elizova K D, Tarasenko V I, Koulintchenko M V, Konstantinov Yu M.

A large set of tRNAs is imported into the plant mitochondria from the cytosol. Besides tRNA import, the mitochondria are capable of uptaking DNA from the cytosol. These two processes may partially overlap, but little is known about which membrane proteins act as carriers for both DNA and RNA. In our work, we studied the role of tRNA carriers in the outer mitochondrial membrane in DNA transfer into the Arabidopsis mitochondria. The outer membrane translocase receptor subunit Tom20-2 and tRNA import-engaged Tric1/Tric2 proteins are involved in the import of short (265 bp), but not long (2.7 kb), DNA fragments. The presence of one of the Tric subunits is sufficient for the normal functioning of the DNA transport channel formed by these proteins. Based on treatment of mitochondria isolated from tric1/tric2 knockout line with antibodies, we suggest that Tric1/2 plays a central role in the import of not only tRNA but also short-length DNA fragments, sharing channel with VDAC1 and Tom40. Thus, our results suggest that Tric1/2 proteins and TOM complex subunits take part in both tRNA and DNA translocation, revealing a new layer of multifunctionality of outer membrane carrier proteins.

Keywords: In vitro transcription; Mitochondrial nucleic acid import; Short DNA fragment; TOM; Tric; tRNA

DOI: https://doi.org/10.1007/s00709-025-02083-9