Increased expression of queuosine synthesizing enzyme, tRNA-guanine transglycosylase, and queuosine levels in tRNA of leukemic cells

Queuosine is a modified nucleoside located at the first position of the tRN A anticodon, which is synthesized by tRNA-guanine transglycosylase (TGT), A lthough the levels of queuosine in cancer cells have been reported to be lo wer than those in normal cells, the expression levels of TGT remain to be d etermined, We determined the expression levels of a subunit of TGT (TGT60KD ). Contrary of our expectations, the results revealed higher levels of expr ession of TGT60KD than that in normal cells, and the level of queuosine in the tRNA fraction corresponded with that of TGT60KD expression. These resul ts suggest the possibilities that the expression levels of TGT60KD regulate TGT activity and the levels of queuosine, and that TGT60KD plays significa nt roles in carcinogenesis. To our knowledge, this is a first report of inc reased expression levels of TGT60KD in human cancer cells.