Abstract
MutT-related proteins, including the Escherichia coli MutT and human MutT homologue 1 (MTH1) proteins, degrade 8-oxo- 7,8-dihydrodeoxyguanosine triphosphate (8-oxo-dGTP) to a monophosphate, thereby preventing mutations caused by the misincorporation of 8-oxoguanine into DNA. Here, we report that human cells have another mechanism for cleaning up the nucleotide pool to ensure accurate DNA replication. The human Nudix type 5 (NUDT5) protein hydrolyses 8-oxo-dGDP to monophosphate with a K(m) of 0.77 microM, a value considerably lower than that for ADP sugars, which were originally identified as being substrates of NUDT5. NUDT5 hydrolyses 8-oxo-dGTP only at very low levels, but is able to substitute for MutT when it is defective. When NUDT5 is expressed in E. coli mutT(-) cells, the increased frequency of spontaneous mutations is decreased to normal levels. Considering the enzymatic parameters of MTH1 and NUDT5 for oxidized guanine nucleotides, NUDT5 might have a much greater role than MTH1 in preventing the occurrence of mutations that are caused by the misincorporation of 8-oxoguanine in human cells.
MeSH terms
- Amino Acid Sequence
- Cloning, Molecular
- DNA Repair Enzymes / chemistry
- DNA Repair Enzymes / genetics
- DNA Repair Enzymes / metabolism*
- DNA Replication
- DNA, Complementary / chemistry
- DNA, Complementary / genetics
- Deoxyguanine Nucleotides / metabolism
- Escherichia coli / genetics
- Escherichia coli / metabolism
- Escherichia coli Proteins / chemistry
- Escherichia coli Proteins / genetics
- Escherichia coli Proteins / metabolism*
- Guanine / analogs & derivatives*
- Guanine / chemistry
- Guanine Nucleotides / chemistry
- Guanine Nucleotides / metabolism*
- Humans
- Kinetics
- Molecular Sequence Data
- Mutation
- Oxidation-Reduction
- Phosphoric Monoester Hydrolases / chemistry
- Phosphoric Monoester Hydrolases / genetics
- Phosphoric Monoester Hydrolases / metabolism*
- Pyrophosphatases / chemistry
- Pyrophosphatases / genetics
- Pyrophosphatases / metabolism*
- Sequence Alignment
Substances
- 8-oxo-7,8-dihydrodeoxyguanosine diphosphate
- DNA, Complementary
- Deoxyguanine Nucleotides
- Escherichia coli Proteins
- Guanine Nucleotides
- 8-hydroxyguanine
- Guanine
- Phosphoric Monoester Hydrolases
- NUDT5 protein, human
- Pyrophosphatases
- mutT protein, E coli
- 8-oxodGTPase
- DNA Repair Enzymes