RNA Methyltransferase (RNMT)

In mammals, 5-prime-terminal caps are formed on nascent pre-mRNAs by the sequential action of 2 enzymes, the bifunctional capping enzyme RNGTT and RNA methyltransferase. RNGTT catalyzes the removal of the gamma-phosphate of the initiating nucleotide and transfers GMP from GTP to the resulting diphosphate end. RNA methyltransferase catalyzes the subsequent N7 methylation of the newly formed termini. The terminal 7-methylguanosine is recognized by cap-binding proteins that facilitate key events in gene expression.The predicted 476-amino acid MET protein contains several conserved motifs known to be required for methyltransferase activity. Recombinant Met exhibited RNA methyltransferase activity in vitro, and formed ternary complexes with RNGTT and the elongating form of RNA polymerase II.