Q-MODIFICATION OF TRANSFER-RNAS IN HUMAN BRAIN-TUMORS

Queuosine (Q nucleoside) is a highly modified guanosine analog and is present only in the first position of the anticodons of tRNA(Tyr), tRN A(His), tRNA(Asn) and tRNA(Asp). The levels of Q in normal human brain and two different types of human brain tumors (meningiomas and astroc ytomas) were determined by using an enzymatic assay method. tRNAs isol ated from tumor tissues contained decreased amounts of Q when compared to tRNAs from normal (i.e. non-tumor) brain tissue. There was a relat ionship between the levels of Q nucleoside and the tumor malignancy in the sense that the deficiency was greater in the highly malignant ast rocytomas compared to meningiomas which are usually benign tumors. Inc reased Q deficiency was also observed in higher grade tumors.