Methylated nucleotides block 5'-terminus of vaccinia virus messenger RNA.

Studies on the nature and location of the methylated nucleotides in mRNA synthesized in vitro by vaccinia virus particles revealed an unusual 5'-terminal structure. Evidence that the pyrophosphate group is blocked by 7-methylguanosine and that both 2'-O-methyl-adenosine and 2'-O-methylguanosine occupy penultimate positions was presented. According to this model, the 5'-termini of vaccinia virus mRNAs are: 7MeG-5'ppp-5'GMepNp and 7MeG-5'AMepNp.