Beyond m6A : TRNA modifications from mechanism to therapeutic engineering

Speaker: Ru-Juan Liu, Shanghai Tech University, China

RNA modifications are essential regulators of RNA structure and function, yet much of our mechanistic understanding of tRNA modifications has historically come from studies in bacteria and yeast. How these modifications are precisely installed, dynamically regulated, and functionally diversified in higher eukaryotes rem ains much less understood. By combining RNA mass spectrometry, high-throughput tRNA seque ncing, and other approaches, our laboratory has systematically investigated tRNA modifications in mammalian cells. We have identified multiple previously uncharacterized tRNA-modifying and demodification enzymes, uncovered dynamic regulation and crosstalk among tR  NA modifications, and revealed unexpected functional diversification of RNA-modifying enzymes during evolution, including expansion of their substrate repertoires from tRNAs to mRNAs and acquisition of non-catalytic functions. Using the m5C methyltransferases NSUN2 and NSUN6 as examples, I will discuss how these enzymes recognize distinct tRNA and mRNA substrates and how substrate specificity shapes their biological functions. Finally, I will highlight how these mechanistic insights can be exploited to engineer therapeutic tRNAs and mRNAs with improved properties.