Guanosine 10 methylation by TRMT11–TRMT112 optimizes human mitochondrial tRNAs for efficient translation [CRAC]

Here, we show that the human RNA methyltransferase TRMT11 and its cofactor TRMT112 are imported into mitochondria via N-terminal targeting signals. Using a recently developed N2-methylguanosine (m2G)-sensitive DNAzyme, we demonstrate that TRMT11 catalytic activity and interaction with TRMT112 are required for installation of m2G at position 10 in 13 mitochondrial (mt-)tRNAs.

The crosslinking profile of TRMT11 on mt-tRNAs experimentally supports a model of the TRMT11–TRMT112–mt-tRNATrp complex in which the THUMP domain contacts the 3′ end of the acceptor stem, and G10 is flipped into the S-adenosylmethionine binding pocket for methylation. Transcriptome-wide mapping reveals that TRMT11 interacts with most nuclear-encoded and mt-tRNAs, but only methylates a subset. In vitro reconstitution of TRMT11–TRM112-mediated methylation defines key structural requirements for m2G10 installation across different mt-tRNAs, and reveals how pathogenic mutations influence this modification.