Accepted name: mRNA (guanine-N7)-methyltransferase
Reaction: S-adenosyl-L-methionine + a 5′-(5′-triphosphoguanosine)-[mRNA] = S-adenosyl-L-homocysteine + a 5′-(N7-methyl 5′-triphosphoguanosine)-[mRNA]
Glossary: a 5′-(5′-triphosphoguanosine)-[mRNA] = G5′ppp5′R-[mRNA]
a 5′-(N7-methyl 5′-triphosphoguanosine)-[mRNA] = m7G5′ppp5′R-[mRNA] = cap0
Other name(s): RNMT (gene name); ABD1 (gene name); messenger ribonucleate guanine 7-methyltransferase; guanine-7-methyltransferase; messenger RNA guanine 7-methyltransferase; S-adenosyl-L-methionine:mRNA (guanine-7-N)-methyltransferase
Systematic name: S-adenosyl-L-methionine:mRNA (guanine-N7)-methyltransferase
Comments: The terminal N7-methylguanosine facilitates gene expression in eukaryotic cells and is recognized by cap-binding proteins.
1.  Ensinger, M.J., Martin, S.A., Paoletti, E. and Moss, B. Modification of the 5′-terminus of mRNA by soluble guanylyl and methyl transferases from vaccinia virus. Proc. Natl. Acad. Sci. USA 72 (1975) 2525–2529. [PMID: 1058472]
2.  Groner, Y., Gilbao, E. and Aviv, H. Methylation and capping of RNA polymerase II primary transcripts by HeLa nuclear homogenates. Biochemistry 17 (1978) 977–982. [PMID: 629955]
3.  Martin, S.A. and Moss, B. Modification of RNA by mRNA guanylyltransferase and mRNA(guanine-7-)methyltransferase from vaccinia virions. J. Biol. Chem. 250 (1975) 9330–9335. [PMID: 1194287]
4.  Martin, S.A., Paoletti, E. and Moss, B. Purification of mRNA guanylyltransferase and mRNA(guanine-7-)methyltransferase from vaccinia virions. J. Biol. Chem. 250 (1975) 9322–9329. [PMID: 1194286]
5.  Mao, X., Schwer, B. and Shuman, S. Yeast mRNA cap methyltransferase is a 50-kilodalton protein encoded by an essential gene. Mol. Cell Biol. 15 (1995) 4167–4174. [PMID: 7623811]
6.  Pillutla, R.C., Yue, Z., Maldonado, E. and Shatkin, A.J. Recombinant human mRNA cap methyltransferase binds capping enzyme/RNA polymerase IIo complexes. J. Biol. Chem. 273 (1998) 21443–21446. [PMID: 9705270]
7.  Tsukamoto, T., Shibagaki, Y., Niikura, Y. and Mizumoto, K. Cloning and characterization of three human cDNAs encoding mRNA (guanine-7-)-methyltransferase, an mRNA cap methylase. Biochem. Biophys. Res. Commun. 251 (1998) 27–34. [PMID: 9790902]
[EC created 1981]
Accepted name: 5′-(N7-methyl 5′-triphosphoguanosine)-[mRNA] diphosphatase
Reaction: a 5′-(N7-methyl 5′-triphosphoguanosine)-[mRNA] + H2O = N7-methylguanosine 5′-phosphate + a 5′-diphospho-[mRNA]
Other name(s): DcpS; m7GpppX pyrophosphatase; m7GpppN m7GMP phosphohydrolase; m7GpppX diphosphatase; m7G5′ppp5’N m7GMP phosphohydrolase
Systematic name: 5′-(N7-methyl 5′-triphosphoguanosine)-[mRNA] N7-methylguanosine 5′-phosphate phosphohydrolase
Comments: The enzyme removes (decaps) the N7-methylguanosine 5-phosphate cap from an mRNA degraded to a maximal length of 10 nucleotides [3,6]. Decapping is an important process in the control of eukaryotic mRNA degradation. The enzyme functions to clear the cell of cap structure following decay of the RNA body [2]. The nematode enzyme can also decap triply methylated substrates, 5′-(N2,N2,N7-trimethyl 5′-triphosphoguanosine)-[mRNA] [4].
1.  Malys, N. and McCarthy, J.E. Dcs2, a novel stress-induced modulator of m7GpppX pyrophosphatase activity that locates to P bodies. J. Mol. Biol. 363 (2006) 370–382. [PMID: 16963086]
2.  Liu, S.W., Rajagopal, V., Patel, S.S. and Kiledjian, M. Mechanistic and kinetic analysis of the DcpS scavenger decapping enzyme. J. Biol. Chem. 283 (2008) 16427–16436. [PMID: 18441014]
3.  Liu, H., Rodgers, N.D., Jiao, X. and Kiledjian, M. The scavenger mRNA decapping enzyme DcpS is a member of the HIT family of pyrophosphatases. EMBO J. 21 (2002) 4699–4708. [PMID: 12198172]
4.  van Dijk, E., Le Hir, H. and Seraphin, B. DcpS can act in the 5′-3′ mRNA decay pathway in addition to the 3′-5′ pathway. Proc. Natl. Acad. Sci. USA 100 (2003) 12081–12086. [PMID: 14523240]
5.  Chen, N., Walsh, M.A., Liu, Y., Parker, R. and Song, H. Crystal structures of human DcpS in ligand-free and m7GDP-bound forms suggest a dynamic mechanism for scavenger mRNA decapping. J. Mol. Biol. 347 (2005) 707–718. [PMID: 15769464]
6.  Cohen, L.S., Mikhli, C., Friedman, C., Jankowska-Anyszka, M., Stepinski, J., Darzynkiewicz, E. and Davis, R.E. Nematode m7GpppG and m3(2,2,7)GpppG decapping: activities in Ascaris embryos and characterization of C. elegans scavenger DcpS. RNA 10 (2004) 1609–1624. [PMID: 15383679]
7.  Wypijewska, A., Bojarska, E., Lukaszewicz, M., Stepinski, J., Jemielity, J., Davis, R.E. and Darzynkiewicz, E. 7-Methylguanosine diphosphate (m7GDP) is not hydrolyzed but strongly bound by decapping scavenger (DcpS) enzymes and potently inhibits their activity. Biochemistry 51 (2012) 8003–8013. [PMID: 22985415]
[EC created 2012, modified 2013]