Gromova I I, Thomsen B, Razin S V
Department of Molecular Biology, University of Aarhus, Denmark.
Proc Natl Acad Sci U S A. 1995 Jan 3;92(1):102-6. doi: 10.1073/pnas.92.1.102.
We have analyzed the long-range distribution of topoisomerase II-mediated cleavages induced in an amplified human c-MYC gene locus in the presence of several antitumor agents. The long-range cleavage patterns were found to be nonrandom and similar for all antitumor drugs tested. Cleavages occurred within several kilobase-long areas (approximately 5 kb) highly accessible to topoisomerase II and separated by extended regions (approximately 70-100 kb) of less accessibility, possibly reflecting the mode of DNA organization into loops along the chromosome. Within the cleavage areas, the patterns of cleavage sites showed a certain dependence on the type of drug used for entrapment of topoisomerase II-DNA complexes. Importantly, distribution of cleavage areas in native chromatin and histone-depleted nuclei was very similar, if not identical, suggesting that the primary target of antitumor agents in vivo is topoisomerase II associated with the high-salt-insoluble nuclear matrix. These data show that matrix-attached DNA is preferentially damaged by topoisomerase II-targeting agents, which may be an important cellular event contributing to drug-induced cell death.
我们分析了在几种抗肿瘤药物存在的情况下，在扩增的人类c-MYC基因位点诱导的拓扑异构酶II介导的切割的长程分布。发现长程切割模式对于所有测试的抗肿瘤药物而言是非随机且相似的。切割发生在拓扑异构酶II高度可及的几个千碱基长的区域（约5 kb）内，并被可及性较低的延伸区域（约70 - 100 kb）隔开，这可能反映了DNA沿染色体组织成环的模式。在切割区域内，切割位点的模式显示出对用于捕获拓扑异构酶II-DNA复合物的药物类型有一定的依赖性。重要的是，天然染色质和组蛋白缺失核中切割区域的分布非常相似，甚至可以说是相同的，这表明体内抗肿瘤药物的主要靶点是与高盐不溶性核基质相关的拓扑异构酶II。这些数据表明，与基质结合的DNA优先被靶向拓扑异构酶II的药物损伤，这可能是导致药物诱导细胞死亡的一个重要细胞事件。
