In vitro synthesis of methylated messenger RNA by the virion-associated RNA polymerase of vesicular stomatitis virus

Purified vesicular stomatitis virus contains an enzyme activity that incorporates the methyl group of S-adenosyl-L-methionine into the messenger RNA products during their synthesis in vitro by the virion-associated transcriptase. The methylation reaction is subject to inhibition by S-adenosyl-L-homocysteine, suggesting the transfer of only the methyl group of S-adenosyl-L-methionine to RNA products. The methyl-labeled RNA products are sensitive to RNAase and alkaline hydrolysis and bind efficiently to oligo-(dT)-cellulose. The methylase activity is further shown to be associated only with the VSV ribonucleoprotein core isolated from virions. The methylation occurs at the 5′ terminal base of the RNA chains with approximately 2 methyl groups incorporated per RNA molecule. Alkaline hydrolysis of the methyl-labeled RNA released a 5′ terminal dinucleotide, consistent with some methylation occurring at the 2′ position of the terminal nucleotide.