QTRT2 is the non-catalytic accessory subunit of the eukaryotic tRNA guanine transglycosylase (TGT) heterodimer 1. While QTRT1 provides catalytic activity, QTRT2 is essential for the enzyme complex to function, with its βEβF-sheet identified as an additional RNA-binding motif that contributes to substrate recognition 2. Together, QTRT1/QTRT2 catalyzes the insertion of queuine into the wobble position (position 34) of tRNAs for Asp, Asn, His, and Tyr, replacing a guanine residue with the hypermodified nucleoside queuosine 3. In humans, these queuosine-modified tRNAs undergo further glycosylation with galactose or mannose 3. QTRT2-dependent Q-modification regulates translational efficiency and cell proliferation, with elevated Q-modification enhancing the translation of ribosomal proteins and promoting faster cell proliferation in both HEK293T and dendritic cells 4. Additionally, Q-modification increases surface presentation of MHC-II in immune cells 4. Dysregulation of Q-modification has been implicated in cancer, inflammatory, and neurological diseases 5. QTRT2 function depends on dietary or microbiome-derived queuine availability, linking tRNA modification to nutritional and microbial factors.