Replication of a site-specific trans-8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B(1) adduct by the exonuclease deficient klenow fragment of DNA polymerase I

Chem Res Toxicol. 2000 Nov;13(11):1158-64. doi: 10.1021/tx000129m.


A 19-mer oligodeoxynucleotide containing a site-specific trans-8, 9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B(1) adduct was prepared and purified. This was used as a template for replication with DNA polymerase I exo(-) (Klenow exo(-)) in vitro. The chemical stability of the modified template strand containing the cationic aflatoxin B(1) adduct was monitored by mass spectrometry. Under the conditions used in these assays, the cationic aflatoxin B(1) adduct remained intact; quantitative conversion to the corresponding formamidopyrimidine adduct was not observed. The results revealed that the cationic guanine AFB(1) N7 adduct blocked translesional DNA synthesis at the adducted site and one nucleotide 3' to the adducted site. Correct incorporation of cytosine opposite the lesion led to blockage, while incorrect incorporation of adenine allowed full-length extension. The in vitro experiments with polymerase I yielded base pair substitutions at the lesion site but not the 5'-neighbor substitutions observed in vivo [Bailey, E. A., Iyer, R. S., Stone, M. P., Harris, T. M., and Essigmann, J. M. (1996) Proc. Natl. Acad. Sci. U.S.A. 93, 1535-1539].

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aflatoxin B1 / analogs & derivatives*
  • Aflatoxin B1 / chemical synthesis
  • Aflatoxin B1 / genetics*
  • Aflatoxin B1 / isolation & purification
  • DNA / biosynthesis
  • DNA / chemistry
  • DNA / genetics
  • DNA Adducts / chemical synthesis
  • DNA Adducts / genetics*
  • DNA Adducts / isolation & purification
  • DNA Polymerase I / metabolism*
  • DNA Replication*
  • Exonucleases / deficiency
  • Exonucleases / metabolism
  • Guanine / analogs & derivatives*
  • Guanine / chemical synthesis
  • Guanine / isolation & purification
  • Oligonucleotides / chemical synthesis
  • Oligonucleotides / genetics*
  • Templates, Genetic


  • DNA Adducts
  • Oligonucleotides
  • aflatoxin B1-DNA adduct
  • Guanine
  • 2,3-dihydro-2-(N(7)-guanyl)-3-hydroxyaflatoxin B1
  • DNA
  • Aflatoxin B1
  • DNA Polymerase I
  • Exonucleases