This modification involves the addition of a methyl group to the 2 hydroxyl (-OH) group of the ribose sugar of RNA molecules. In contrast with the mA modification, it is the ribose sugar, a part of the backbone rather than the base that is altered. It is present in various kinds of cellular RNA, providing coding and structural support. 2-O-methylation of viral RNA is often accompanied by the addition of an inverted N-7methylguanosine to the 5 end on the phosphate group. These modifications regulate important functions of viral RNA such as metabolism and immune system interactions.
Different viruses have their mechanisms for acquiring this modification. Cytoplasmic RNA viruses like flaviridae and coronaviruses encode the required to catalyze cap formation reactions, with some needing one enzyme for the 5' cap and 2-O-methylation while others require two enzymes like poxviruses. Others, like influenza virus can hijack the methylguanosine caps from host cell mRNA and be preferentially translated.