There are several identified methylation modifications in eukaryotic messenger RNA (mRNA), such as N(7)-methylguanosine (m(7)G) at the cap, N(6)-methyl-2'-O-methyladenosine (m(6)Am), 2'-O-methylation (Nm) within the cap and the internal positions, and internal N(6)-methyladenosine (m(6)A) and 5-methylcytosine (m(5)C).