Following an environmental carcinogen N2-dG adduct through replication

Elucidating blockage and bypass in a high-fidelity DNA polymerase

Pingna Xu, Lida Oum, Lorena S. Beese, Nicholas E. Geacintov, Suse Broyde

Research output: Contribution to journalArticle

Abstract

We have investigated how a benzo[a]pyrene-derived N2-dG adduct, 10S(+)-trans-anti-[BP]-N2-dG ([BP]G*), is processed in a well-characterized Pol I family model replicative DNA polymerase, Bacillus fragment (BF). Experimental results are presented that reveal relatively facile nucleotide incorporation opposite the lesion, but very inefficient further extension. Computational studies follow the possible bypass of [BP]G* through the pre-insertion, insertion and post-insertion sites as BF alternates between open and closed conformations. With dG* in the normal B-DNA anti conformation, BP seriously disturbs the polymerase structure, positioning itself either deeply in the pre-insertion site or on the crowded evolving minor groove side of the modified template, consistent with a polymerase-blocking conformation. With dG* in the less prevalent syn conformation, BP causes less distortion: it is either out of the pre-insertion site or in the major groove open pocket of the polymerase. Thus, the syn conformation can account for the observed relatively easy incorporation of nucleotides, with mutagenic purines favored, opposite the [BP]G* adduct. However, with the lesion in the BF post-insertion site, more serious distortions caused by the adduct even in the syn conformation explain the very inefficient extension observed experimentally. In vivo, a switch to a potentially error-prone bypass polymerase likely dominates translesion bypass.

Original languageEnglish (US)
Pages (from-to)4275-4288
Number of pages14
JournalNucleic Acids Research
Volume35
Issue number13
DOIs
StatePublished - Jul 2007

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Environmental Carcinogens
DNA-Directed DNA Polymerase
Bacillus
Nucleotides
B-Form DNA
Purines

ASJC Scopus subject areas

  • Genetics

Cite this

Following an environmental carcinogen N2-dG adduct through replication : Elucidating blockage and bypass in a high-fidelity DNA polymerase. / Xu, Pingna; Oum, Lida; Beese, Lorena S.; Geacintov, Nicholas E.; Broyde, Suse.

In: Nucleic Acids Research, Vol. 35, No. 13, 07.2007, p. 4275-4288.

Research output: Contribution to journalArticle

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