| Project/Area Number |
10670859
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Radiation science
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| Research Institution | Nagasaki University |
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Principal Investigator |
IHARA Makoto Nagasaki University, School of Medicine, Assistant, 医学部, 助手 (60175213)
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| Co-Investigator(Kenkyū-buntansha) |
OKUMURA Yutaka Nagasaki University, School of Medicine, Professor, 医学部, 教授 (00073130)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1998: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | DNA-PK / Ku70 / 80 / DNA double strand break / Heat treatment / DNA-PK活性 / 熱ショック蛋白質 / DNA二本鎖切断の修復 / X線 |
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| Research Abstract |
The mechanism of thermoradiosensitization was studied.
Double stranded DNA dependent protein kinase (DNA-PK) consist of DNA-PKcs (catalytic subunit) and Ku70/80 heterodimer (DNA double strand break end binding subunit). When DNA double strand break was occurred, Ku70/80 heterodimer bind to DNA double strand break end and then bind DNA-PKcs. This active form of DNA-PK phosphorylate a variety of proteins including p53, XRCC4 proteins, etc.
We analyzed the heat sensitivity of DNA-PK activity in hybrid cells and the possible restoration of this activity with extracts from scid cells (defective in DNA-PKcs). Heat treatment of cells was performed in a water bath at 44℃. The cell extract from scid cells or sxi-3 cells was added to heat-treated hybrid cell extracts, and the DNA-PK activity was assayed. When hybrid cells were heated at 44℃ for 15 min, DNA-PK activity was reduced to undetectable levels. The decreased DNA-PK activity could be restored in concentration-dependent manner with the addition of scid cell extract. This result indicates that Ku70/80, but not Ku70 alone, could restore heat-inactivated DNA-PK.
DNA double strand breaks was repaired by two phase, namely fast repair and slow repair in hybrid cells. But in scid cells, DNAdsb was repaired by the single phase (slow repair). The fast repair was inactivated by heat treatment. Considering that DNA-PK activity was heat sensitive, these results indicate that the fast repair was maintained by DNA-PK activity.
From these results, thermoradiosensitization was the result of heat inactivation of DNA-PK.
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