A 7-methylguanine tRNA methylase present in crown-gall cells but absent in normal Parthenocissus tricuspidata L. cells

Abstract

Pure yeast tRNA 1 Ala was methylated in vitro in the presence of S-adenosyl [Me- 14C] methionine and enzyme preparations from normal or tumor cells of Parthenocissus tricuspidata L. The [Me- 14C] tRNA 1 Ala was hydrolyzed by pancreatic ribonuclease and the resulting oligonucleotides were analyzed using classical techniques of nucleotide sequence determination. The enzyme preparations from normal and tumor cells transform the adenylic residue present in the Tψ loop of tRNA 1 Ala into m 1A. But only the tumor cells contain an m 7G methylase which methylates the guanylic residue located in the extra-loop at position 46 from the 5′ end of tRNA 1 Ala.