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

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 ? anomeric configuration in addition to canonical ? 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 ? 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 ? anomer of Fapy-dG. Environ. Mol. Mutagen. 58:182-189, 2017. © 2017 Wiley Periodicals, Inc.

SUBMITTER: Sha Y 

PROVIDER: S-EPMC5476229 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature