Selective Methylation of Nucleosides¹

Abstract

Phenylalanine tRNA from Ehrlich ascites cells and Novikoff hepatoma has been found to contain 1-methyl-guanosine (5a) ². The tRNA methyl transferases of e.g., normal liver tissue do not produce this N-methylated nucleoside. Indeed the urine of various human cancer patients has recently been found to contain unusually large amounts of certain partially methylated nucleosides and in amounts sufficient to serve as markers for evaluating disease progression.³ In general, a variety of methylated nucleosides⁴ have been discovered in animal RNA especially in tRNA and mRNA, and syntheses of these modified nuclesodies has been attempted using such reagents as methyl iodide,⁵ diazomethane,⁶ dimethyl sulfate,⁷ and trimethyl phosphate.⁸