S-Space College of Medicine/School of Medicine (의과대학/대학원) Pharmacology (약리학전공) Journal Papers (저널논문_약리학전공)
Exogenous 8-oxo-dG is not utilized for nucleotide synthesis but enhances the accumulation of 8-oxo-Gua in DNA through error-prone DNA synthesis
- Kim, Ja-Eun; Hyun, Jin-Won; Hayakawa, Hiroshi; Choi, Seongwon; Choi, Jinhee; Chung, Myung-Hee
- Issue Date
- Mutation Research 596 (2006) 128–136
- Base Sequence; Cell Line, Tumor; DNA Primers; DNA Repair; DNA Replication/*genetics; Deoxyguanosine/*analogs & derivatives/pharmacokinetics; Deoxyribonucleosides/biosynthesis; Guanine/*analogs & derivatives/metabolism; Humans; *Mutation
- 7,8-Dihydro-8-oxoguanine (8-oxo-Gua) and its nucleoside in cytosol are derived from the repair of oxidative DNA and the cleanup of oxidatively damaged DNA precursors, respectively. While the harmful effects of 8-oxo-Gua present in DNA have been studied extensively, few have reported its effects on cytosolic function. Our previous study showed that the addition of 8-oxo-dG to culture media caused an accumulation of 8-oxo-Gua in nuclear DNA in several leukemic cells including KG-1, which lack 8-oxoguanine glycosylase 1 (OGG1) activity due to mutational loss. However, the mechanism underlying 8-oxo-Gua level increases in DNA has not been addressed. In this study, we elucidated the metabolic fate of 8-oxo-Gua-containing nucleotide and the effect of exogenous 8-oxo-dG on DNA synthesis in KG-1 cells. We found that 8-oxo-dGMP was rapidly dephosphorylated to 8-oxo-dG rather than phosphorylated to 8-oxo-dGDP, thus indicating that 8-oxo-Gua-containing molecule is not used as a substrate for DNA synthesis in KG-1 cells. In fact, radiolabeled 8-oxo-dG was incubated but radioactivity was not detected in nuclear DNA of KG-1 cells, showing that 8-oxo-dG is not directly incorporated into DNA. Interestingly, the activity of DNA polymerase beta, which synthesize DNA with low fidelity increased in KG-1 cells treated with 8-oxo-dG, whereas the expression of DNA polymerase alpha decreased. In addition, the accumulation of 8-oxo-Gua in KG-1 DNA was completely inhibited by a specific inhibitor of DNA polymerase beta. Thus, our findings address that the insertion of 8-oxo-dG into KG-1 DNA is not due to the direct incorporation of exogenous 8-oxo-dG, but rather to the inaccurate incorporation of endogenous 8-oxo-dGTP by DNA polymerase beta. It further suggests that 8-oxo-dG in the cytosol may function as an active molecule itself and perturb the well-defined DNA synthesis.
- 0027-5107 (Print)
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