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DNA replication fidelity with 8-oxodeoxyguanosine triphosphate
Y I Pavlov1, D T Minnick, S Izuta
1Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Biochemistry
|April 19, 1994
Summary
Oxidative stress generates 8-oxodeoxyguanosine (8-oxo-dGTP), a mutagenic compound. This study shows 8-oxo-dGTP causes DNA replication errors, leading to mutations, but some enzymes can proofread these errors.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Oxidative metabolism produces mutagenic compounds like 8-oxodeoxyguanosine.
- The mutagenic potential of 8-oxodeoxyguanosine triphosphate (8-oxo-dGTP) during DNA replication is not fully understood.
Purpose of the Study:
- To investigate the mutagenic potential of 8-oxo-dGTP during DNA replication in vitro and in eukaryotic systems.
- To determine the fidelity of DNA polymerases in incorporating 8-oxo-dGTP and whether this misincorporation can be proofread.
Main Methods:
- In vitro DNA replication using M13mp2 DNA and various DNA polymerases (exonuclease-deficient Klenow, T4, Thermus thermophilus).
- Sequence analysis of DNA mutants to identify misincorporation events.
- SV40 origin-dependent replication in HeLa cell extracts to assess eukaryotic system mutagenicity.
Main Results:
- 8-oxo-dGTP decreases DNA synthesis fidelity across multiple DNA polymerases, primarily causing adenine to cytosine (A-->C) transversions.
- Proofreading-proficient T4 DNA polymerase showed lower 8-oxo-dGTP misincorporation than its proofreading-deficient counterpart, indicating proofreading capability.
- In HeLa cell extracts, 8-oxo-dGTP was significantly more mutagenic than normal dGTP, causing A.T-->C.G transversions.
Conclusions:
- 8-oxo-dGTP is a potent mutagen that can be misincorporated during DNA replication, leading to specific transversions.
- The fidelity of DNA synthesis and the potential for proofreading against 8-oxo-dGTP incorporation are enzyme-dependent.
- 8-oxo-dGTP poses a mutagenic risk in both prokaryotic and eukaryotic replication systems.