Tomura T, van Lancker J L
Department of Pathology and Radiation Oncology, School of Medicine, University of California, Los Angeles 90024.
J Rheumatol. 1988 Jan;15(1):59-64.
The interactions of procainamide with DNA were studied by neutral and alkaline sucrose gradient sedimentation and sequential action of 2 enzymes: a mammalian repair endonuclease and bacterial DNA polymerase I. Sucrose gradient sedimentation shows that in the absence of photosensitization, the interaction of procainamide with DNA did not modify DNA sedimentation in alkaline or neutral sucrose gradients. In contrast, when a photosensitized DNA procainamide mixture was placed on sucrose gradients, the peak appearing on alkaline sucrose gradient after treatment with endonuclease was shifted toward the lower molecular weights, indicating that strand breaks had developed in the photosensitized procainamide DNA. Incubation of a [32P] labeled photosensitized procainamide-DNA complex with a repair endonuclease and DNA polymerase I released the label in the acid soluble fraction, indicating that only the photosensitized procainamide-DNA complex was susceptible to the endonucleolytic attack. There was only negligible release of the label in the acid soluble fraction without exposure of the DNA-procainamide mixture to light. The incorporation into DNA of [3H]-TTP (tritium labeled triphosphates) in presence of DNA polymerase I was inhibited when the photosensitized procainamide-DNA complex was used as substrate. However, after treatment of the photosensitized DNA complex with the repair endonuclease, the incorporation of [3H]-TTP was increased and reached values close to that observed with DNA unexposed to light, suggesting that the endonuclease functions as a repair enzyme.
通过中性和碱性蔗糖梯度沉降以及两种酶（一种哺乳动物修复核酸内切酶和细菌DNA聚合酶I）的顺序作用，研究了普鲁卡因酰胺与DNA的相互作用。蔗糖梯度沉降表明，在没有光致敏的情况下，普鲁卡因酰胺与DNA的相互作用不会改变DNA在碱性或中性蔗糖梯度中的沉降。相反，当将光致敏的DNA - 普鲁卡因酰胺混合物置于蔗糖梯度上时，用核酸内切酶处理后碱性蔗糖梯度上出现的峰向较低分子量移动，表明在光致敏的普鲁卡因酰胺 - DNA中发生了链断裂。将[32P]标记的光致敏普鲁卡因酰胺 - DNA复合物与修复核酸内切酶和DNA聚合酶I一起孵育，会使酸溶性部分释放出标记物，这表明只有光致敏的普鲁卡因酰胺 - DNA复合物易受核酸内切酶攻击。在DNA - 普鲁卡因酰胺混合物未暴露于光的情况下，酸溶性部分中标记物的释放可以忽略不计。当使用光致敏的普鲁卡因酰胺 - DNA复合物作为底物时，在DNA聚合酶I存在下[3H]-TTP（氚标记的三磷酸核苷）掺入DNA的过程受到抑制。然而，在用修复核酸内切酶处理光致敏的DNA复合物后，[3H]-TTP的掺入增加并达到接近未暴露于光的DNA所观察到的值，这表明核酸内切酶起到修复酶的作用。
