Differential m(6)A, m(6)A(m), and m(1)A Demethylation Mediated by FTO in the Cell Nucleus and Cytoplasm

FTO, the first RNA demethylase discovered, mediates the demethylation of internal N-6-methyladenosine (m(6)A) and N-6, 2-O-dimethyladenosine (m(6)A(m)) at the +1 position from the 5' cap in mRNA. Here we demonstrate that the cellular distribution of FTO is distinct among different cell lines, affecting the access of FTO to different RNA substrates. We find that FTO binds multiple RNA species, including mRNA, snRNA, and tRNA, and can demethylate internal m(6)A and cap m(6)A(m) in mRNA, internal m(6)A in U6 RNA, internal and cap m(6)A(m) in snRNAs, and N-1-methyladenosine (m(1)A) in tRNA. FTO-mediated demethylation has a greater effect on the transcript levels of mRNAs possessing internal m(6)A than the ones with cap m(6)A(m) in the tested cells. We also show that FTO can directly repress translation by catalyzing m(1)A tRNA demethylation. Collectively, FTO-mediated RNA demethylation occurs to m(6)A and m(6)A(m) in mRNA and snRNA as well as m(1)A in tRNA.