title: LC-MS/MS identification and yeast polymerase eta bypass of a novel gamma-irradiation-induced intrastrand cross-link lesion G[8-5]C.
abstract: Reactive oxygen species can give rise to intrastrand cross-link lesions, where two neighboring nucleobases are covalently bonded. Here, we employed LC-MS/MS and demonstrated for the first time that gamma irradiation of a synthetic duplex oligodeoxyribonucleotide can give rise to an intrastrand cross-link lesion G[8-5]C, where the C8 carbon atom of guanine and the C5 carbon atom of its 3'-neighboring cytosine are covalently bonded. We also carried out in vitro replication studies of a substrate containing a site-specifically incorporated G[8-5]C, and our results showed that yeast Saccharomyces cerevisiae DNA polymerase eta (pol eta) was able to replicate past the cross-link lesion. Steady-state kinetic analyses for nucleotide incorporation by pol eta showed that the 3'-cytosine moiety of the cross-link did not significantly affect either the efficiency or the fidelity of nucleotide incorporation. The 5' guanine portion of the cross-link lesion, however, markedly reduced both the efficiency and the fidelity of nucleotide incorporation; the insertion of dGMP or dAMP was slightly favored over the insertion of the correct nucleotide, dCMP, which was in turn favored over the insertion of dTMP. The above results support that the oxidative cross-link lesion, if not repaired, can be mutagenic.
authors.affiliation: Environmental Toxicology Graduate Program, University of California, Riverside, California 92521-0403, USA.
authors.forename: Chunang
authors.initials: C
authors.lastname: Gu
authors.forename: Yinsheng
authors.initials: Y
authors.lastname: Wang
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D003596:Cytosine / Q000737:chemistry*; D004249:DNA Damage; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D003838:Deoxyadenine Nucleotides / Q000378:metabolism; D003848:Deoxyguanine Nucleotides / Q000378:metabolism; D005720:Gamma Rays; D006147:Guanine / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods; D009692:Nucleic Acid Heteroduplexes / Q000528:radiation effects*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013938:Thymidine Monophosphate; D000099270:Y-Family DNA Polymerases
chemical_list: D003596:Cytosine; D004259:DNA-Directed DNA Polymerase; D003838:Deoxyadenine Nucleotides; D003848:Deoxyguanine Nucleotides; D006147:Guanine; D009692:Nucleic Acid Heteroduplexes; D029701:Saccharomyces cerevisiae Proteins; D013938:Thymidine Monophosphate; C012873:2'-deoxy-5'-adenosine monophosphate; C007257:2'-deoxyguanosine 5'-phosphate; C112338:Rad30 protein; D000099270:Y-Family DNA Polymerases