碩士 / 國立臺灣海洋大學 / 生物科技研究所 / 101 / DNA mismatch repair (MMR) of simple mispairs and small insertion-deletion loops (IDLs) in eukaryotes is initiated by the binding of MutS homolog 2 (MSH2)-MSH6 heterodimer to mismatched nucleotides. Mercury (Hg2+) is a toxic heavy metal and Hg2+ is the major form of inorganic Hg in water and soil, and Hg2+ has been shown to cause DNA damage in aquatic organisms and inhibit radiation-induced DNA repair in human lymphocytes. This research explored if Hg2+ could impair MSH2/MSH6-mediated mismatch recognition in zebrafish (Danio rerio) embryos. Whole-mount in situ hybridization showed the inability of Hg2+ at 1 to 3 μM to disturb msh2/msh6 mRNA production in zebrafish tissues after exposing embryos at 1 h post fertilization (hpf) to Hg2+ for 4 or 9 h. In contrast, DNA mismatch binding activities in zebrafish embryos were much more sensitive to Hg2+, as G-T mismatch and 2-IDL binding activities were suppressed to only 20% of control by 3 μM Hg2+ following a 9-h exposure based on band shift assay. Inhibition of mismatch recognition capacity in zebrafish extracts incubated directly with 3 μM, but not with 1 μM Hg2+, revealed the preferential targeting of Hg2+ at higher levels to MSH2/MSH6-DNA interactions. Pretreatment of embryos with the antioxidant BHT failed to protect against mismatch recognition suppressed by either 1 or 3 μM Hg2+ in zebrafish embryos, suggesting the independence of reactive oxygen species with Hg-suppressed mismatch binding. This research showed that Hg2+ may impair MMR by primarily disturbing the interactions between MSH proteins and mismatched nucleotides.
| Identifer | oai:union.ndltd.org:TW/101NTOU5613003 |
| Date | January 2013 |
| Creators | Shao-Chiang Hsu, 徐少強 |
| Contributors | Todd Hsu, 許濤 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 47 |
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