Witham AA, Verwey AMR, Sproviero M, Manderville RA, Sharma P, Wetmore SD. Chlorine functionalization of a model phenolic C8-guanine adduct increases conformational rigidity and blocks extension by a Y-family DNA polymerase.
Chem Res Toxicol 2015;
28:1346-56. [PMID:
26004422 DOI:
10.1021/acs.chemrestox.5b00143]
[Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Certain phenoxyl radicals can attach covalently to the C8-site of 2'-deoxyguanosine (dG) to afford oxygen-linked C8-dG adducts. Such O-linked adducts can be chemically synthesized through a nucleophilic displacement reaction between a phenolate and a suitably protected 8-Br-dG derivative. This permits the generation of model O-linked C8-dG adducts on scales suitable for insertion into oligonucleotide substrates using solid-phase DNA synthesis. Variation of the C8-aryl moiety provides an opportunity to derive structure-activity relationships on adduct conformation in duplex DNA and replication bypass by DNA polymerases. In the current study, the influence of chlorine C8-dG functionalization on in vitro DNA replication by Klenow fragment exo(-) (Kf(-)) and the Y-family polymerase (Sulfolobus solfataricus P2 DNA polymerase IV (Dpo4)) has been determined. Model O-linked C8-dG adducts derived from the pentachlorophenoxyl radical ([PCP]G) and 2,4,6-trichlorophenoxyl radical ([TCP]G) were inserted into the reiterated G3-position of the NarI sequence (12-mer, NarI(12); and 22-mer, NarI(22)), which is a known hotspot for frameshift mutations mediated by N-linked polycyclic C8-dG adducts in bacterial mutagenesis. Within the NarI(12) duplex, the unsubstituted C8-phenoxy-dG ([PhO]G) adduct adopts a minimally perturbed B-form helix. Chlorination of [PhO]G to afford [PCP]G does not significantly change the adduct conformation within the NarI(12) duplex, as predicted by molecular dynamics simulations. However, when using NarI(22) for DNA synthesis in vitro, the chlorinated [PCP]G and [TCP]G lesions significantly block DNA replication by Kf(-) and Dpo4, whereas [PhO]G is readily bypassed. These findings highlight the impact that chlorine substituents impart to bulky C8-dG lesions.
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