Tumour-specific phenylalanine tRNA contains two supernumerary methylated bases

Abstract
Every malignant tumor examined contains aberrant tRNA methyltransferases and a few tRNA which are absent from the normal tissue of origin. To determine whether tumor-specific tRNA have different modifications from those in normal tissue, the most frequently occurring tumor-specific isoaccepting tRNA was purified from 2 malignant tissues. The isoaccepting phenylalanine tRNA from Novikoff hepatoma and Ehrlich ascites cells contains 2 supernumerary methylated bases. One of these, 1-methylguanine, is absent from the phenylalanine tRNA of normal rat, mouse, rabbit and calf liver. An increase in the levels of 5-methylcytidine and dihydrouridine was also detected.