Mapping messenger RNA methylations at single base resolution

The messenger RNA (mRNA) methylations in mammalian cells have been found to contain N 6 -methyladenosine (m 6 A), N 6 -2′- O -dimethyladenosine (m 6 Am), 7-methylguanosine (m 7 G), 1-methyladenosine (m 1 A), 5-methylcytosine (m 5 C), and 2′- O -methylation (2′-OMe). Their regulatory functions in control of mRNA fate and gene expression are being increasingly uncovered. To unambiguously understand the critical roles of mRNA methylations in physiological and pathological processes, mapping these methylations at single base resolution is highly required. Here, we will review the progresses made in methylation sequencing methodologies developed mainly in recent two years, with an emphasis on chemical labeling-assisted single base resolution methods, and discuss the problems and prospects as well.