Nucleic Acids Research, 1977, Vol. 4, No. 6 1853-1872
© 1977
Articles |
Alterations of tRNA modification in mammalian systems: the effect of ethionine
Department of Pharmacology, State University of New York, Downstate Medical Center Brooklyn, NY 11203, USA
Received February 16, 1977. The relationship between the modification of tRNA and its ability to act as a substrate for homologous tRNA modification enzymes in vitro was studied. The tRNA extracted from the livers of rats was active as a substrate for in vitro methylation with extracts from normal rat liver 19 h after treatment with L-ethionine (35 mg/100 g/24 h). After 4 weeks of feeding a diet containing 0.25% DL-ethionine, the tRNA was a poor substrate for methylation in vitro, even though it was deficient in methylated nucleosides. Only 18%. and 7% of the available sites could be methylated after 67 h and 4 weeks, respectively, of ethionine treatment
3-(3-amino-3-carboxypropyl)uridine, a nucleoside that is also synthesized from S-adenosylmethionine, was assayed in individual tRNAs by their reactivity with the N-hydroxysuccinimide ester of phenoxyacetic acid. The reactivity of tRNAIIe, tRNAAsn, and tRNAThr was decreased by treatment with ethionine at 67 h as well as at 2 and 4 weeks, although no difference could be detected at 19 h.