2005 Fiscal Year Final Research Report Summary
Inhibition of DNA-PK activity and radio-sensitization induced by single strand DNA
| Project/Area Number |
15390357
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | The University of Tokyo |
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Principal Investigator |
HOSOI Yoshio The University of Tokyo, Graduate School of Medicine, Associate Professor, 大学院・医学系研究科, 助教授 (50238747)
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| Project Period (FY) |
2003 – 2005
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| Keywords | ionizing radiation / DNA-PK / single strand DNA / DNA double strand breaks / suramin |
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| Research Abstract |
Phosphorothioate oligonucleotides and suramin bind to heparin binding proteins including DNA polymerases, and inhibit their functions. In the present study, we report inhibition of DNA-dependent protein kinase (DNA-PK) activity by phosphorothioate oligonucleotides and suramin. Inhibitory effect of phosphorothioate oligonucleotides on DNA-PK activity was increased with length and reached a plateau at 36-mer. The base composition of phosphorothioate oligonucleotides did not affect the inhibitory effect. The inhibitory effect by phosphorothioate oligodeoxycytidine 36-mer can be about 200-fold greater than that by the phosphodiester oligodeoxycytidine 36-mer. The inhibitory effect was also observed with purified DNA-PK, which suggests direct interaction between DNA-PK and phosphorothioate oligonucleotides. DNA-PK will have different binding positions for double-stranded DNA and phosphorothioate oligodeoxycytidine 36-mer because they were not competitive in DNA-PK activation. Suramin sensit
… More
ized cells to X-radiation in a dose-dependent fashion and longer exposure to suramin before X-irradiation resulted in more efficient sensitization. The dose-modifying factors calculated from the survival curves were 1.18 in LM217 cells and 1.37 in MDA-MB-468 cells. Suramin did not sensitized scid cells that had no DNA-dependent protein kinase activity. Suramin inhibited DNA-dependent protein kinase activity in vitro and in vivo. The concentration of suramin resulting in 50% inhibition in vitro was 1.7 μM in LM217 cells and 2.4 μM in MDA-MB-468 cells. Exposure of LM217 and MDA-MB-468 cells to suramin did not affect the level of Ku70 or Ku80, but it increased the level of DNA-PKcs. Suramin did not sensitize LM217 or MDA-MB-468 cells to UV radiation. Exposure to suramin inhibited the repair of DNA double-strand breaks caused by 50 Gy irradiation. Suramin's effects were not caused by accumulation of cells in a specific phase of the cell cycle. These results suggest that suramin sensitizes cells to ionizing radiation by inhibiting DNA-dependent protein kinase activity. Less
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Research Products
(28 results)
