Cloning and expression of cDNA for a human enzyme that hydrolyzes 8-oxo-dGTP, a mutagenic substrate for DNA synthesis.
8-Oxoguanine (8-oxo-7, 8-dihydroguanine) is produced in DNA, as well as in nucleotide pools of cells, by active oxygen species normally formed during cellular metabolic processes. 8-Oxoguanine nucleotide can pair with cytosine and adenine nucleotides at almost equal efficiencies, and transversion mutation ensues. Human cells contain enzyme activity, which hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, and this enzyme is responsible for preventing misincorporation of 8-oxoguanine into DNA. We purified this particular human enzyme to physical homogeneity and determined a partial amino acid sequence. We then cloned the cDNA for human 8-oxo-dGTPase and examined its nucleotide sequence. The human protein comprises 156 amino acid residues and has some sequence homology with the Escherichia coli MutT protein, which has a distinct 8-oxo-dGTPase activity. When the human cDNA was expressed in E. coli mutT- mutant cells, there was a significant amount of 8-oxo-dGTPase activity. In such cells, the frequency of spontaneous mutation was greatly reduced. We propose that the human 8-oxo-dGTPase protects genetic information from the untoward effects of endogenous oxygen radicals.
Sakumi
K
K
Medical Institute of Bioregulation, Faculty of Science, Kyushu University, Fukuoka, Japan.
Furuichi
M
M
Tsuzuki
T
T
Kakuma
T
T
Kawabata
S
S
Maki
H
H
Sekiguchi
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004260:DNA Repair; D045643:DNA Repair Enzymes; D018076:DNA, Complementary / Q000235:genetics; D003848:Deoxyguanine Nucleotides / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009153:Mutagens / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics*; D011994:Recombinant Proteins; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D018076:DNA, Complementary; D003848:Deoxyguanine Nucleotides; D009153:Mutagens; D010455:Peptides; D011994:Recombinant Proteins; C078206:8-oxodeoxyguanosine triphosphate; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases; C078207:8-oxodGTPase; D045643:DNA Repair Enzymes