Inhibition of DNA-PK activity and radio-sensitization induced by single strand DNA

硫代寡核苷酸和苏拉明结合肝素结合蛋白，包括DNA聚合酶，并抑制其功能。在本研究中，我们报道了硫代寡核苷酸和苏拉明对dna依赖性蛋白激酶（DNA-PK）活性的抑制作用。硫代寡核苷酸对DNA-PK活性的抑制作用随着长度的增加而增加，在36 mer时达到平稳期。硫代寡核苷酸的碱基组成不影响抑菌效果。硫代寡脱氧胞苷36-mer的抑制作用可比磷酸二酯寡脱氧胞苷36-mer大约200倍。纯化的DNA-PK也有抑制作用，这表明DNA-PK与硫代寡核苷酸直接相互作用。双链DNA和硫代寡脱氧胞苷36-mer在DNA- pk激活过程中不存在竞争关系，因此DNA- pk具有不同的结合位置。苏拉明敏感性…更多的细胞以剂量依赖的方式接受x射线照射，x射线照射前更长的苏拉明暴露导致更有效的敏化。根据生存曲线计算的剂量修饰因子在LM217细胞为1.18，在MDA-MB-468细胞为1.37。苏拉明对没有dna依赖性蛋白激酶活性的scid细胞没有致敏作用。苏拉明在体外和体内均抑制dna依赖性蛋白激酶活性。苏拉明对LM217细胞的体外抑制浓度为1.7 μM，对MDA-MB-468细胞的体外抑制浓度为2.4 μM。苏拉明对LM217和MDA-MB-468细胞的Ku70和Ku80水平没有影响，但使DNA-PKcs水平升高。苏拉明不使LM217或MDA-MB-468细胞对紫外线辐射敏感。暴露于苏拉明可抑制50 Gy辐照引起的DNA双链断裂的修复。苏拉明的作用不是由细胞周期特定阶段的细胞积累引起的。这些结果表明苏拉明通过抑制dna依赖性蛋白激酶活性使细胞对电离辐射敏感。少

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