Information on EC 3.6.1.62 - 5'-(N7-methylguanosine 5'-triphospho)-[mRNA] hydrolase and Organism(s) Xenopus laevis and UniProt Accession Q6TEC1

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X29

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X29 protein

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5'-(N7-methylguanosine 5'-triphospho)-[mRNA] N7-methylguanosine-5'-diphosphate phosphohydrolase

Decapping of mRNA is a critical step in eukaryotic mRNA turnover. The enzyme is unable to cleave a free cap structure (m7GpppG) [3]. The enzyme from Vaccinia virus is synergistically activated in the presence of Mg2+ and Mn2+ [5].

m7G5'ppp5'-NO38 mRNA + H2O

m7GDP + 5'-phospho-NO38 mRNA

removes m7G and m227G caps from RNAs, rendering them substrates for 5'-3' exonucleases for degradation in vivo. The metal identity determines both the efficiency of decapping and the RNA substrate specificity. In Mg2+ the protein hydrolyzes the 5' cap from only one RNA substrate: U8 small nucleolar RNA. In the presence of Mn2+ or Co2+ all RNAs are substrates and the decapping efficiency is higher. The metal that binds the X29/H29K proteins in vivo may determine whether these decapping proteins function solely as a negative regulator of ribosome biogenesis or can decap a wider variety of nuclear-limited RNAs

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m7G5'ppp5'-U3 snoRNA + H2O

m7GDP + U3 snoRNA + H2O

removes m7G and m227G caps from RNAs, rendering them substrates for 5'-3' exonucleases for degradation in vivo. The metal identity determines both the efficiency of decapping and the RNA substrate specificity. In Mg2+ the protein hydrolyzes the 5' cap from only one RNA substrate: U8 small nucleolar RNA. In the presence of Mn2+ or Co2+ all RNAs are substrates and the decapping efficiency is higher. The metal that binds the X29/H29K proteins in vivo may determine whether these decapping proteins function solely as a negative regulator of ribosome biogenesis or can decap a wider variety of nuclear-limited RNAs

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m7G5'ppp5'-U8 snoRNA + H2O

m7GDP + 5'-phospho-U8 snoRNA

2 entries

additional information

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X29 has decapping activity and releases m7GDP from full-length U8 RNA. The NUDIX domain in X29 is required for cap cleavage and release of m7GDP from U8 RNA. X29 can cleave the m227G cap present on U8 RNA in vivo

670221

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m7G5'ppp5'-U8 snoRNA + H2O

m7GDP + 5'-phospho-U8 snoRNA

removes m7G and m227G caps from RNAs, rendering them substrates for 5'-3' exonucleases for degradation in vivo

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Co2+

the metal identity determines both the efficiency of decapping and the RNA substrate specificity. In Mg2+ the protein hydrolyzes the 5' cap from only one RNA substrate: U8 small nucleolar RNA. In the presence of Mn2+ or Co2+ all RNAs are substrates and the decapping efficiency is higher

Mg2+

the metal identity determines both the efficiency of decapping and the RNA substrate specificity. In Mg2+ the protein hydrolyzes the 5' cap from only one RNA substrate: U8 small nucleolar RNA. In the presence of Mn2+ or Co2+ all RNAs are substrates and the decapping efficiency is higher. The metal that binds the X29/H29K proteins in vivo may determine whether these decapping proteins function solely as a negative regulator of ribosome biogenesis or can decap a wider variety of nuclear-limited RNAs

Mn2+

the metal identity determines both the efficiency of decapping and the RNA substrate specificity. In Mg2+ the protein hydrolyzes the 5' cap from only one RNA substrate: U8 small nucleolar RNA. In the presence of Mn2+ or Co2+ all RNAs are substrates and the decapping efficiency is higher. The metal that binds the X29/H29K proteins in vivo may determine whether these decapping proteins function solely as a negative regulator of ribosome biogenesis or can decap a wider variety of nuclear-limited RNAs

m7GDP

although product inhibition by released m7GDP may occur, the amount of m7GDP released from RNA by X29 in these decapping reactions is well below the amount found to inhibit X29 decapping activity in the assay

8

assay at

8.5

assay at

37

assay at

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670221, 715488, 716934

SwissProt

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NUD16_XENLA

212

0

24350

Swiss-Prot

Show Sequence

other Location (Reliability: 2)

30000

2 * 30000, SDS-PAGE

60000

gel filtration

dimer

2 * 30000, SDS-PAGE

crystallizes as a homodimeric apoenzyme. Structure of X29 complexes with m7GpppA and pppG in the presence of Mn+2

E150Q

mutant protein is inactive under all conditions

E89Q

mutant protein is inactive under all conditions

E92Q

mutant displays weak decapping activity under the standard decapping conditions in both Mg2+ and Mn2+, a significant increase in hydrolysis in the presence of higher concentrations of metal

E92Q/E93Q

mutation displays less than 5% decapping activity in Mn2+ under the optimized decapping conditions. A 10fold increase in the amount of metal present in the reaction (to 1 mM Mn2+) only marginally increases the efficiency of cap hydrolysis

E93Q

mutation displays less than 5% decapping activity in Mn2+ under the optimized decapping conditions. A 10fold increase in the amount of metal present in the reaction (to 1 mM Mn2+) only marginally increases the efficiency of cap hydrolysis

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cloned into a His-tagged expression vector, overexpressed in Escherichia coli

670221

Ghosh, T.; Peterson, B.; Tomasevic, N.; Peculis, B.A.

Xenopus U8 snoRNA binding protein is a conserved nuclear decapping enzyme

Mol. Cell

13

817-828

2004

Homo sapiens, Xenopus laevis (Q6TEC1)

15053875