EC Number   |
General Information |
Reference |
|---|
   3.6.1.74 | evolution |
CTL1 is the second member of the yeast RNA triphosphatase family. Enzyme CTL1 resembles the C-terminus of Cet1, which has RNA triphosphatase activity |
-, 762030 |
| 3.6.1.74 | evolution |
gene CES5 is identical to gene CET1, which encodes the RNA triphosphatase component of the yeast capping apparatus |
-, 761894 |
| 3.6.1.74 | evolution |
metazoans including humans contain a separate cap methyltransferase (RNA guanine-7-methyltransferase, RNMT), but the RNA 5'-triphosphatase and guanylyltransferase activities are contained as N- and C-terminal domains in a bifunctional capping enzyme (RNGTT) encoded by a single gene |
761214 |
| 3.6.1.74 | evolution |
RNA 5'-triphosphatase activity is widely distributed among prokaryotes, eukaryotes, and viruses |
-, 762030 |
| 3.6.1.74 | evolution |
the nucleotide sequences of hCAP1a and hCAP1b are identical from the 5' flanking region to codon 503, but are entirely different thereafter. The N-terminal portion of the predicted amino acid sequence contains the motif of the tyrosine specific protein phosphatase active site, [LIVMF]-H-C-x(2)-G-x(3)-[STC]-[STAG]-x-[LIVMFY]. The C-terminal portion of the protein is highly homologous to the known mRNA guanylyltransferases and contains all the motifs, i.e. motifs I, III, IIIa, IV, V, VI, and P, which are commonly observed in viral and cellular mRNA guanylyltransferases except that the motif VI is missing in hCAP1b |
760471 |
| 3.6.1.74 | malfunction |
ceg1-25 mutation of the yeast mRNA guanylyltransferase (capping enzyme) causes a temperature-sensitive growth defect. Truncated mutant protein Cet1(201-549) has RNA triphosphatase activity, heterodimerizes with and stimulates Ceg1 in vitro, and suffices when expressed in single copy for cell growth in vivo. The more extensively truncated mutant Cet1(246-549) also has RNA triphosphatase activity but fails to stimulate Ceg1 in vitro and is lethal when expressed in single copy in vivo |
-, 761894 |
| 3.6.1.74 | malfunction |
deletion mutant analysis of hCAP1a shows that the N-terminal 213 amino acid fragment containing a tyrosine-specific protein phosphatase motif catalyzes the RNA 5'-triphosphatase activity, and the C-terminal 369 amino acid fragment exhibits the mRNA guanylyltransferase activity. When RNA 5'-triphosphatase activity is assayed using [gamma-32 P]pppG-RNA, mutant His-hCAP1a(1-213) releases [32P]phosphate, while no [32P]phosphate is released by mutant hCAP1a(229-597). Furthermore, the N-terminal half molecule, hCAP1a(1-213) exhibits no NTPase activity, indicating that this half molecule still retains the specificity for RNA |
760471 |
| 3.6.1.74 | malfunction |
HCE1A and HCE1B have been identified as variants of HCE1. Hce1p possesses both TPase and GTase activities, but Hce1a and Hce1b proteins have deletions within the ORF and lack GTase activity. The failure of Hce1a and Hce1b proteins to complement an Saccharomyces cerevisiae cet1DELTA null mutation may be due to the failure of complex formation between the yeast GTase and the human capping enzyme |
761075 |
| 3.6.1.74 | metabolism |
during transcription by RNA polymerase II, a cap structure is formed on the 5'-termini of most nascent nuclear pre-mRNAs. Capping of mRNA has been shown to be important for the stabilization, processing, nuclear export, and efficient translation of mRNA. Capping involves at least three enzymes called mRNA 5'-triphosphatase (TPase), mRNA 5'-guanylyltransferase (GTase), and cap methyltransferase (MTase). TPase converts the 5'-triphosphate end of a nascent RNA chain into a diphosphate end, and GTase transfers the GMP moiety of GTP to the newly produced 5'-diphosphate end of RNA to form a blocking structure. Thereafter, MTase attaches a methyl group to the 7 position of the terminal guanosine of RNA. As GTase and TPase are essential for the synthesis of the core cap structure, they are called mRNA 5'-capping enzymes. The physical association of mRNA 5'-guanylyltransferase (GTase) and mRNA 5'-triphosphatase (TPase) is essential for the function of the capping enzyme in vivo |
-, 761075 |
| 3.6.1.74 | metabolism |
subunit Cet1 is a monomer in solution, it binds with recombinant subunit Ceg1 (EC 2.7.7.50) in vitro to form a Cet1-Ceg1 heterodimer. The interaction of Cet1 with Ceg1 elicits over 10fold stimulation of the guanylyltransferase activity of Ceg1, the Cet1-Ceg1 interaction is essential. Potential for regulating mRNA cap formation through protein-protein interactions |
-, 761894 |
