Nucleic Acids Research Advance Access originally published online on February 14, 2008
Nucleic Acids Research 2008 36(7):2174-2181; doi:10.1093/nar/gkn062
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Nucleic Acids Research, 2008, Vol. 36, No. 7 2174-2181
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Trace amounts of 8-oxo-dGTP in mitochondrial dNTP pools reduce DNA polymerase 
replication fidelity
1Laboratory of Molecular Genetics and Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC 27709 and 2Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331-7305, USA
*To whom correspondence should be addressed. Tel: +1 919 541 2644; Fax: +1 919 541 7613; Email: kunkel{at}niehs.nih.gov
Received December 19, 2007. Revised January 23, 2008. Accepted January 30, 2008.
Replication of the mitochondrial genome by DNA polymerase 
requires dNTP precursors that are subject to oxidation by reactive oxygen species generated by the mitochondrial respiratory chain. One such oxidation product is 8-oxo-dGTP, which can compete with dTTP for incorporation opposite template adenine to yield A-T to C-G transversions. Recent reports indicate that the ratio of undamaged dGTP to dTTP in mitochondrial dNTP pools from rodent tissues varies from 
1:1 to >100:1. Within this wide range, we report here the proportion of 8-oxo-dGTP in the dNTP pool that would be needed to reduce the replication fidelity of human DNA polymerase . When various in vivo mitochondrial dNTP pools reported previously were used here in reactions performed in vitro, 8-oxo-dGTP was readily incorporated opposite template A and the resulting 8-oxo-G-A mismatch was not proofread efficiently by the intrinsic 3' exonuclease activity of pol . At the dNTP ratios reported in rodent tissues, whether highly imbalanced or relatively balanced, the amount of 8-oxo-dGTP needed to reduce fidelity was <1% of dGTP. Moreover, direct measurements reveal that 8-oxo-dGTP is present at such concentrations in the mitochondrial dNTP pools of several rat tissues. The results suggest that oxidized dNTP precursors may contribute to mitochondrial mutagenesis in vivo, which could contribute to mitochondrial dysfunction and disease.
Present address: J. Tyson McDonald, Roy E. Coats Laboratories, Radiation Biology Experimental Division, Department of Radiation Oncology, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
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