THUMPD3 is a catalytic subunit of the THUMPD3-TRM112 methyltransferase complex that specifically mediates S-adenosyl-L-methionine-dependent N2-methylation of guanosine nucleotides in tRNAs 1. The enzyme primarily catalyzes m2G6 modification in tRNAs and represents one of the major tRNA (guanine-N2)-methyltransferases 1. Additionally, THUMPD3 catalyzes N2-methylation of guanosine at position 7 of tRNA(Trp) 1. Beyond tRNA modification, THUMPD3 plays important roles in cellular processes including protein synthesis and cell proliferation 1. In cancer contexts, THUMPD3 demonstrates oncogenic properties by regulating alternative splicing of extracellular matrix transcripts, particularly maintaining expression of pro-tumor Fibronectin-1 isoforms in lung cancer cells 2. THUMPD3 depletion significantly impairs cancer cell fitness, reducing proliferation and migration 2. In pancreatic cancer, the THUMPD3/TRMT112 complex promotes cell growth and autophagy through TFEB translation regulation via impaired m2G modification of tRNA(Leu) 3. The enzyme is upregulated in multiple cancer types and correlates with poor prognosis, suggesting its potential as a therapeutic target 3.