Published online 16 January 2004
Nucleic Acids Research, 2004, Vol. 32, No. 1 397-405
© 2004 Oxford University Press
Nucleotide incorporation by human DNA polymerase 
opposite benzo[a]pyrene and benzo[c]phenanthrene diol epoxide adducts of deoxyguanosine and deoxyadenosine
Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, National Institutes of Health, DHHS, PO Box 12233, Research Triangle Park, NC 27709, USA and 1 Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, MD 20892, USA
*To whom correspondence should be addressed. Tel: +1 919 541 4792; Fax: +1 919 541 7613; Email: copelan1{at}niehs.nih.gov
Permanent address:
Maria A. Graziewicz, Institute of Biochemistry and Biophysics, Polish Academy of Science, 02-106 Warsaw, Poland
Mitochondria are major cellular targets of benzo[a]pyrene (BaP), a known carcinogen that also inhibits mitochondrial proliferation. Here, we report for the first time the effect of site-specific N2-deoxyguanosine (dG) and N6-deoxyadenosine (dA) adducts derived from BaP 7,8-diol 9,10-epoxide (BaP DE) and dA adducts from benzo[c]phenanthrene 3,4-diol 1,2-epoxide (BcPh DE) on DNA replication by exonuclease-deficient human mitochondrial DNA polymerase (pol 
) with and without the p55 processivity subunit. The catalytic subunit alone primarily misincorporated dAMP and dGMP opposite the BaP DE–dG adducts, and incorporated the correct dTMP as well as the incorrect dAMP opposite the DE–dA adducts derived from both BaP and BcPh. In the presence of p55 the polymerase incorporated all four nucleotides and catalyzed limited translesion synthesis past BaP DE–dG adducts but not past BaP or BcPh DE–dA adducts. Thus, all these adducts cause erroneous purine incorporation and significant blockage of further primer elongation. Purine misincorporation by pol opposite the BaP DE–dG adducts resembles that observed with the Y family pol 
. Blockage of translesion synthesis by these DE adducts is consistent with known BaP inhibition of mitochondrial (mt)DNA synthesis and suggests that continued exposure to BaP reduces mtDNA copy number, increasing the opportunity for repopulation with pre-existing mutant mtDNA and a resultant risk of mitochondrial genetic diseases.
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