The Functions of N 6 -Methyladenosine in Nuclear RNAs.

N6 -methyladenosine (m6 A) is one of the most common modifications in both eukaryotic and prokaryotic mRNAs. It has been experimentally confirmed that m6 A methylation is involved in the regulation of stability and translation of various mRNAs. Until recently, the majority of m6 A-related studies have been focused on the cytoplasmic functions of this modification. Here, we review new data on the role of m6 A in several key biological processes taking place in the cell nucleus, such as transcription, chromatin organization, splicing, nuclear-cytoplasmic transport, and R-loop metabolism. Based on analysis of these data, we suggest that m6 A methylation of nuclear RNAs is another level of gene expression regulation which, together with DNA methylation and histone modifications, controls chromatin structure and functioning in various biological contexts.