| View Larger Image | TCDD-induced homologous recombination: the role of the Ah receptor versus oxidative DNA damage [An article from: Mut.Res.-Genetic Toxicology and Environmental Mutagenesis] | Digitalby C.Y.Y. Chan (Author), P.M. Kim (Author), L.M. Winn (Author)
| List Price: | $8.95 | | | Available: | Available for download now |
| | Binding: | Digital | | Publisher: | Elsevier | | Publication Date: | September 12, 2004 |
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Product Description
This digital document is a journal article from Mut.Res.-Genetic Toxicology and Environmental Mutagenesis, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.Description: The environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) elicits numerous biological responses including carcinogenicity. The molecular mechanism by which TCDD exerts its tumorigenic effects is unclear, since it does not directly damage DNA. TCDD-initiated toxicity can be mediated by the aryl hydrocarbon receptor (AhR) pathway and/or via increased oxidative stress. DNA damage, including DNA oxidation, can induce DNA double-strand breaks, which can be repaired through homologous recombination. Excessive DNA double-strand breaks may promote aberrant DNA recombination, which can lead to detrimental genetic changes and ultimately to carcinogenesis. TCDD has been shown to induce homologous recombination but the molecular mechanism mediating these events are unknown. To investigate the role of the AhR and oxidative DNA damage in mediating TCDD-induced homologous recombination we used a Chinese hamster ovary (CHO) cell line containing a neo direct repeat recombination substrate (CHO 3-6). CHO 3-6 cells were exposed to TCDD (50, 500 or 1000 pM) in the presence or absence of an AhR antagonists (0.1@mM @a-naphthoflavone (@a-NF)) for 6 or 24h and 2 weeks later homologous recombination frequencies were determined by counting the number of neo expressing, G418-resistant colonies per live cells plated. TCDD-initiated DNA oxidation was determined by measuring the formation of 8-hydroxy-2'-deoxyguanosine via HPLC and electrochemical detection. Exposure to 500 pM TCDD for 24h significantly increased the frequency of homologous recombination. Southern blot analysis on G418-resistant colonies determined that TCDD induced both conservative gene conversion events and deletion events. DNA oxidation was not increased in cells exposed to TCDD for either 6 or 24h. However, @a-naphthoflavone exposure resulted in a significant decrease in TCDD-induced homologous recombination frequency. These results suggest that TCDD-initiated homologous recombination in CHO 3-6 cells is mediated by the AhR and not via increased oxidative stress. |
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