Targeted deletion of the genes encoding NTH1 and NEIL1 DNA N-glycosylases reveals the existence of novel carcinogenic oxidative damage to DNA

Michael K. Chan, Maria T. Ocampo-Hafalla, Vladimir Vartanian, Pawel Jaruga, Güldal Kirkali, Karen L. Koenig, Stuart Brown, R. Stephen Lloyd, Miral Dizdaroglu, George W. Teebor

Research output: Contribution to journalArticle

80 Scopus citations

Abstract

We have generated a strain of mice lacking two DNA N-glycosylases of base excision repair (BER), NTH1 and NEIL1, homologs of bacterial Nth (endonuclease three) and Nei (endonuclease eight). Although these enzymes remove several oxidized bases from DNA, they do not remove the well-known carcinogenic oxidation product of guanine: 7,8-dihydro-8-oxoguanine (8-OH-Gua), which is removed by another DNA N-glycosylase, OGG1. The Nth1-/-Neil1-/- mice developed pulmonary and hepatocellular tumors in much higher incidence than either of the single knockouts, Nth1-/- and Neil1-/-. The pulmonary tumors contained, exclusively, activating GGT → GAT transitions in codon 12 of K-ras of their DNA. Such transitions contrast sharply with the activating GGT → GTT transversions in codon 12 of K-ras of the pathologically similar pulmonary tumors, which arose in mice lacking OGG1 and a second DNA N-glycosylase, MUTY. To characterize the biochemical phenotype of the knockout mice, the content of oxidative DNA base damage was analyzed from three tissues isolated from control, single and double knockout mice. The content of 8-OH-Gua was indistinguishable among all genotypes. In contrast, the content of 4,6-diamino-5-formamidopyrimidine (FapyAde) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua) derived from adenine and guanine, respectively, were increased in some but not all tissues of Neil1-/- and Neil1-/-Nth1-/- mice. The high incidence of tumors in our Nth1-/-Neil1-/- mice together with the nature of the activating mutation in the K-ras gene of their pulmonary tumors, reveal for the first time, the existence of mutagenic and carcinogenic oxidative damage to DNA which is not 8-OH-Gua.

Original languageEnglish (US)
Pages (from-to)786-794
Number of pages9
JournalDNA Repair
Volume8
Issue number7
DOIs
StatePublished - Jul 4 2009

Keywords

  • Base excision repair
  • Cancer
  • K-ras
  • Mouse
  • NEIL1
  • NTH1

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Chan, M. K., Ocampo-Hafalla, M. T., Vartanian, V., Jaruga, P., Kirkali, G., Koenig, K. L., Brown, S., Lloyd, R. S., Dizdaroglu, M., & Teebor, G. W. (2009). Targeted deletion of the genes encoding NTH1 and NEIL1 DNA N-glycosylases reveals the existence of novel carcinogenic oxidative damage to DNA. DNA Repair, 8(7), 786-794. https://doi.org/10.1016/j.dnarep.2009.03.001