Error-prone replication bypass of the imidazole ring-opened formamidopyrimidine deoxyguanosine adduct

Yan Sha, Irina Minko, Chanchal K. Malik, Carmelo J. Rizzo, Robert (Stephen) Lloyd

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

Addition of hydroxyl radicals to the C8 position of 2′-deoxyguanosine generates an 8-hydroxyguanyl radical that can be converted into either 8-oxo-7,8-dihydro-2′-deoxyguanosine or N-(2-deoxy-d-pentofuranosyl)-N-(2,6-diamino-4-hydroxy-5-formamidopyrimidine) (Fapy-dG). The Fapy-dG adduct can adopt different conformations and in particular, can exist in an unnatural α anomeric configuration in addition to canonical β configuration. Previous studies reported that in 5′-TGN-3′ sequences, Fapy-dG predominantly induced G → T transversions in both mammalian cells and Escherichia coli, suggesting that mutations could be formed either via insertion of a dA opposite the 5′ dT due to primer/template misalignment or as result of direct miscoding. To address this question, single-stranded vectors containing a site-specific Fapy-dG adduct were generated to vary the identity of the 5′ nucleotide. Following vector replication in primate cells (COS7), complex mutation spectra were observed that included ∼3–5% G → T transversions and ∼14–21% G → A transitions. There was no correlation apparent between the identity of the 5′ nucleotide and spectra of mutations. When conditions for vector preparation were modified to favor the β anomer, frequencies of both G → T and G → A substitutions were significantly reduced. Mutation frequencies in wild-type E. coli and a mutant deficient in damage-inducible DNA polymerases were significantly lower than detected in COS7 and spectra were dominated by deletions. Thus, mutagenic bypass of Fapy-dG can proceed via mechanisms that are different from the previously proposed primer/template misalignment or direct misinsertions of dA or dT opposite to the β anomer of Fapy-dG. Environ. Mol. Mutagen. 58:182–189, 2017.

Original languageEnglish (US)
Pages (from-to)182-189
Number of pages8
JournalEnvironmental and Molecular Mutagenesis
Volume58
Issue number4
DOIs
StatePublished - May 1 2017

Keywords

  • COS7
  • DNA lesion
  • Escherichia coli
  • mutagenesis
  • oxidative damage

ASJC Scopus subject areas

  • Epidemiology
  • Genetics(clinical)
  • Health, Toxicology and Mutagenesis

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