RNA triphosphatase

In molecular biology, RNA 5'-triphosphatases (RTPases) are phosphatases that cleave the 5'-terminal γ-β phosphoanhydride bond of nascent messenger RNA molecules, enabling the addition of a five-prime cap as part of post-transcriptional modifications. RTPases generate 5'-diphosphate-ended mRNA and a phosphate ion from 5'-triphosphate-ended precursor mRNA. mRNA guanylyltransferase then adds a backwards guanosine monophosphate (GMP) group from GTP, generating pyrophosphate, and mRNA (guanine-N7-)-methyltransferase methylates the guanine to form the final 5'-cap structure.^{[1][2][3][4][5]}

There are two families of RTPases known so far:

• the metal-dependent family. Yeast,^[4][6][7] protozoan, and viral^[4][8] RTPases require a metal co-factor for their activity, which is most often either Mg²⁺ or Mn²⁺. This class of enzymes is also able to hydrolyze free nucleoside triphosphates in the presence of either Mn²⁺ or Co²⁺.^[1]
• the metal-independent family. These groups do not require metals for their activity, and some enzymes have been shown to be inactivated in the presence of metal ions. These enzymes are very much similar to protein tyrosine phosphatases in their structure and mechanism.^[9][10][11] This family includes RTPases from mammals, plants, and other higher eukaryotes,^[8] and is structurally and mechanistically different from the metal-dependent RTPase family.^[4][5][7]

See also

• Transcription (genetics)
• Five-prime cap

References

1. Gross, Christian H; Shuman, Stewart (September 1998). "Characterization of a Baculovirus-Encoded RNA 5'-Triphosphatase". Journal of Virology. 72 (9): 7057–7063. Retrieved 6 December 2014.
2. Ho, C Kiong; Schwer, Beate; Shuman, Stewart (September 1998). "Genetic, Physical, and Functional Interactions between the Triphosphatase and Guanylyltransferase Components of the Yeast mRNA Capping Apparatus". Molecular and Cellular Biology. 18 (9): 5189–5198. Retrieved 6 December 2014.
3. Shuman, Stewart (2000). "Structure, mechanism, and evolution of the mRNA capping apparatus". Progress in Nucleic Acid Research and Molecular Biology. 66: 1–40. doi:10.1016/s0079-6603(00)66025-7. Retrieved 6 December 2014.
4. Takagi, Toshimitsu; Moore, Christine R; Diehn, Felix; Buratowski, Stephen (June 1997). "An RNA 5′-Triphosphatase Related to the Protein Tyrosine Phosphatases". Cell. 89 (6): 867–873. doi:10.1016/S0092-8674(00)80272-X. Retrieved 6 December 2014.
5. Wen, Yingxia; Yue, Zhenyu; Shatkin, Aaron J (13 October 1998). "Mammalian capping enzyme binds RNA and uses protein tyrosine phosphatase mechanism". Proceedings of the National Academy of Sciences. 95 (21): 12226–12231. doi:10.1073/pnas.95.21.12226. PMC 22813. PMID 9770468. Retrieved 6 December 2014.
6. Bisaillon, Martin; Bougie, Isabelle (22 June 2003). "Investigating the Role of Metal Ions in the Catalytic Mechanism of the Yeast RNA Triphosphatase". Journal of Biological Chemistry. 278 (36): 33963–33971. doi:10.1074/jbc.M303007200. Retrieved 6 December 2014.
7. Lima, Christopher D.; Wang, Li Kai; Shuman, Stewart (November 1999). "Structure and Mechanism of Yeast RNA Triphosphatase". Cell. 99 (5): 533–543. doi:10.1016/S0092-8674(00)81541-X. Retrieved 6 December 2014.
8. Karpe, Yogesh A; Lole, Kavita S (30 June 2010). "RNA 5'-Triphosphatase Activity of the Hepatitis E Virus Helicase Domain". Journal of Virology. 84 (18): 9637–9641. doi:10.1128/JVI.00492-10. Retrieved 6 December 2014.
9. Barford, D; Flint, A J; Tonks, N K (11 March 1994). "Crystal structure of human protein tyrosine phosphatase 1B". Science. 263 (5152): 1397–1404. doi:10.1126/science.8128219. PMID 8128219. Retrieved 6 December 2014.
10. Denu, John M; Dixon, Jack E (January 1998). "Protein tyrosine phosphatases: mechanisms of catalysis and regulation". Current Opinion in Chemical Biology. 2 (5): 633–641. doi:10.1016/S1367-5931(98)80095-1. Retrieved 6 December 2014.
11. Deshpande, Tarangini; Takagi, Toshimitsu; Hao, Luning; Buratowski, Stephen; Charbonneau, Harry (4 June 1999). "Human PIR1 of the Protein-tyrosine Phosphatase Superfamily Has RNA 5'-Triphosphatase and Diphosphatase Activities". Journal of Biological Chemistry. 274 (23): 16590–16594. doi:10.1074/jbc.274.23.16590. Retrieved 6 December 2014.