title: In vitro replication of primer-templates containing benzo[a]pyrene adducts by exonuclease-deficient Escherichia coli DNA polymerase I (Klenow fragment): effect of sequence context on lesion bypass.
abstract: The presence of benzo[a]pyrene diol epoxide (B[a]PDE) adducts in DNA is known to interfere with DNA replication. Kinetic studies of nucleotide insertion by exonuclease-deficient E. coli DNA polymerase I (Klenow fragment) across from either the (+)-trans- or the (+)-cis-B[a]P-N(2)-dG adduct in the 5'-CGT-3' sequence context indicated that the rate of nucleotide incorporation followed the order: dAMP > dGMP > dTMP > dCMP, which did not correlate with the mutational spectrum observed for these adducts in this sequence in E. coli (mostly G-->A transitions). Interestingly, a kinetic analysis of extension past the adduct showed that, unlike other sequences studied, the primer-template was extended best when dT was positioned at the 3'-terminus of the primer across from either a (+)-trans- or a (+)-cis-B[a]P-N(2)-dG adduct. In contrast, when the (+)-trans-B[a]P-N(2)-dG adduct was positioned in the 5'-TGC-3' sequence context, which gives predominantly G-->T mutations in E. coli, extension was detectable only when dA was positioned across from the adduct. These data provide the first in vitro evidence that may explain why G-->A transitions, rather than the G-->T transversions found in other sequences, are preferred in the 5'-CGT-3' sequence in vivo.
authors.affiliation: Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
authors.forename: Y O
authors.initials: YO
authors.lastname: Alekseyev
authors.forename: L J
authors.initials: LJ
authors.lastname: Romano
mesh_terms: D001483:Base Sequence; D001564:Benzo(a)pyrene / Q000737:chemistry* / Q000378:metabolism; D018736:DNA Adducts / Q000737:chemistry* / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004261:DNA Replication; D004926:Escherichia coli / Q000201:enzymology; D066298:In Vitro Techniques; D007700:Kinetics
chemical_list: D018736:DNA Adducts; D017931:DNA Primers; D001564:Benzo(a)pyrene; D004256:DNA Polymerase I