TRMT10C (tRNA methyltransferase 10C) is a mitochondrial enzyme with dual functions in tRNA processing and modification. As a core component of the mitochondrial ribonuclease P complex (mtRNase P), TRMT10C partners with HSD17B10/MRPP2 and PRORP/MRPP3 to cleave the 5'-ends of mitochondrial pre-tRNAs 1. The TRMT10C-HSD17B10 subcomplex serves as a tRNA maturation platform that recognizes conserved mitochondrial tRNA elements, including the anticodon loop, and positions tRNAs for proper processing 1. TRMT10C catalyzes N1-methylation of guanosine and adenosine at position 9 (m1G9 and m1A9) in mitochondrial tRNAs, modifications essential for tRNA stability and function 2. The enzyme also facilitates 3'-end processing by ELAC2, particularly for structurally degenerate mitochondrial tRNAs that lack canonical structures 2. Beyond tRNA processing, TRMT10C methylates MT-ND5 mRNA at N1-adenosine residues 3. Disease relevance includes combined oxidative phosphorylation deficiency 30, reflecting its critical role in mitochondrial function. Under pathological conditions, nuclear translocation of TRMT10C can contribute to cellular dysfunction through aberrant mRNA modifications 4. The enzyme represents an essential component of mitochondrial RNA processing machinery required for proper oxidative phosphorylation.