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Son, Mi-Young,Jun, Hyun-Ik,Lee, Kwang-Geun,Demple, Bruce,Sung, Jung-Suk Informa UK (TaylorFrancis) 2009 Journal of toxicology and environmental health. Pa Vol.72 No.21
<P>Numerous environmental carcinogens involve radical formation interacting with DNA to produce 2-deoxyribonolactone (dL), a major type of oxidized abasic site, implicated in DNA strand breaks, mutagenesis, and formation of covalent DNA-protein cross-links (DPC). Studies showed major dL-specific DPC occurred due to reactions with DNA polymerase beta (Polbeta) dependent on native conformation, while other DPC formed involved nonenzymatic reactions of DNA binding proteins with dL lesions. Polbeta appeared to play a major role in alleviating the cytotoxic effects of neocarzinostatin, which was used as a dL-producing agent. When a duplex DNA containing a dL at a site-specific position was incubated with purified histones, DPC were formed between dL and each histone protein, including H1, H2A, H2B, H3, and H4. Comparative kinetic analysis of DPC formation with histones and Polbeta revealed two distinct mechanisms of dL-mediated DPC formation. The rate of DPC formation with Polbeta was approximately two orders of magnitude higher than that with various histone proteins. These results indicate that catalytic activity of Polbeta mediates rapid DPC formation between dL and this DNA repair enzyme, whereas nonenzymatic reactions of dL with histones form DPC more slowly. The abundance of histones and their constant interaction with DNA may nevertheless yield significant levels of DPC with dL, as biomarkers of dL-induced cytotoxicity. Overall, data suggest that occurrence of dL-mediated DPC with histones may contribute to the genotoxic effects of dL in DNA.</P>
Expression analysis of the fpr (ferredoxin-NADP^(+) reductase) gene in Pseudomonas putida KT2440
Lee, Yun-Ho,Samuel Pe?a-Llopis ^(b,1),Kang, Yoon-Suk,Shin, Hyeon-Dong,Bruce Demple,Eugene L. Madsen,Jeon, Che-Ok,Park, Woo-Jun Plant molecular biology and biotechnology research 2005 Plant molecular biology and biotechnology research Vol.2005 No.
The ferredoxin-NADP^(+) reductase (fpr) participates in cellular defense against oxidative damage. The fpr expression in Pseudomonas putida KT2440 is induced by oxidative and osmotic stresses. FinR, a LysR-type transcriptional factor near the fpr gene in the P. putida KT2440 genome, is required for induction of the fpr under both conditions. We have shown that the fpr and finR gene products can counteract the effects of oxidative and osmotic stresses. Interestingly, FinR-independent expression occurs either during a long period of incubation with paraquat or with high concentrations of oxidative stress agent. This result indicates that there may be additional regulators present in the P. putida KT2440 genome. In contrast to in vivo expression kinetics of fpr from the plant pethogen, Pseudomonas syringae, the fpr gene from P. putida KT2440 exhibited unusually prolonged expression after oxidative stress. Transcriptional fusion and Northern blot analysis studies indicated that the FinR is negatively autoregulated. Expression of the fpr promoter was higher in minimal media than in rich media during exponential phase growth. Consistent with this result. the fpr and finR mutants had a long lag phase in minimal media in contrast to wild-type growth characteristics. Antioxidants such as ascorbate could increase the growth rate of all tested strains in minimal media. This result confirmed that P. putida KT2440 experienced more oxidative stress during exponential growth in minimal media than in rich media. Endogenous promoter activity of the fpr gene is much higher during exponential growth than during stationary growth. These findings demonstrate new relationships between fpr, finR, and the physiology of oxidative stress in P. putida KT2440. ⓒ 2005 Elsevier Inc. All rights reserved.