Preparation of Human Nuclear RNA m⁶A Methyltransferases and Demethylases and Biochemical Characterization of Their Catalytic Activity

N(6)-Methyladenosine (m(6)A) represents the most prevalent internal modification in messenger and long noncoding RNAs. There has been a surge of interest toward understanding the biological significance of m(6)A modification. In this chapter, we describe the methods for biochemically studying the recently uncovered m(6)A methyltransferases (METTL3 and METTL14) and demethylases (FTO and ALKBH5). How to express these proteins, perform their biochemistry reactions against various RNA probes, and characterize the methylation and demethylation activity will be discussed.