Charp P A
Methods Enzymol. 1987;139:715-30.
These results of these assays, therefore, suggested that calmodulin functions by modulating the initial step of excision repair of UV-damaged DNA. The initial step in this process is the endonuclease function. The reasoning follows these lines of thought: Dimer chromatography indicates that incision and excision occur albeit at a decreased rate. If no excision occurs, the dimer region will remain bound to the DNA and there would be no difference between the control and treated samples. Therefore any difference detected should be due to a decrease in the incision step of repair. The photolysis assay also indicates a decrease in the incision step. Since the patch size between the control and treated cultures were identical within experimental error (64 vs 72 bases), there is no inhibition of polymerase activity. If excision were affected during the photolysis assay, it is possible that the free region of the incised strand could be used as a primer strand and the repaired DNA could have a higher molecular weight than the control strand. This was not observed. Finally, the cytosine arabinoside procedures indicated that less cytosine arabinoside molecules were incorporated into the damaged regions. Since the photolysis assay indicated that the polymerase reaction was not affected, this would indicate that less initial sites were available for repair, that is, less nicks were available indicative of decreased endonuclease activity.
因此，这些检测结果表明，钙调蛋白通过调节紫外线损伤DNA切除修复的起始步骤发挥作用。这一过程的起始步骤是核酸内切酶功能。推理如下：二聚体色谱法表明切口和切除过程虽然速率降低但仍会发生。如果没有切除发生，二聚体区域将仍然与DNA结合，并且对照样品和处理样品之间不会有差异。因此，检测到的任何差异都应归因于修复切口步骤的减少。光解检测也表明切口步骤减少。由于在实验误差范围内（64对72个碱基）对照培养物和处理培养物之间的片段大小相同，因此不存在对聚合酶活性的抑制。如果在光解检测过程中切除受到影响，那么有可能切开链的自由区域可以用作引物链，并且修复后的DNA可能具有比对照链更高的分子量。但并未观察到这种情况。最后，阿糖胞苷实验表明，较少的阿糖胞苷分子掺入到损伤区域。由于光解检测表明聚合酶反应未受影响，这表明可用于修复的起始位点较少，也就是说，较少的切口表明核酸内切酶活性降低。
