Methylated messenger RNA synthesis in vitro by purified reovirus

Purified human reovirus contains RNA methylase activity in addition to an RNA polymerase. Virions incubated under appropriate conditions in the presence of S-adenosyl-L-methionine synthesize mRNA that is specifically methylated in the 5'-terminal guanosine. Alkaline digestion of the methylated RNA released a 5'-terminal dinucleotide, ppG'pCp, indicating that the guanosine contains 2'-O-methylribose. The possible roles of methylation in viral and cellular mRNA function is discussed.