Jaxel C, Kohn K W, Pommier Y
Laboratory of Molecular Pharmacology, National Institutes of Health, Bethesda, MD 20892.
Nucleic Acids Res. 1988 Dec 9;16(23):11157-70. doi: 10.1093/nar/16.23.11157.
Camptothecin is an antitumor drug, which is a specific inhibitor of eukaryotic topoisomerase I. Enzyme inhibition is related to the stabilization of cleavable complexes between topoisomerase I and DNA. The genomic and DNA sequence localization of L1210 topoisomerase I-mediated DNA breaks produced by camptothecin were determined in the SV40 genome. DNA cleavage was predominantly single-stranded and localized in selective regions of the DNA. A major cleavage site was found at nucleotide 4995 on the coding strand in the early transcription region. The DNA sequence was determined at prominent cleavage sites (nucleotides 127 and 199 in the two 72 bp repeats and nucleotide 4955). A DNA consensus sequence 5'-GATG-3' was found in SV40 DNA. Cleavage occurred between the T and the G and topoisomerase I was linked to the 3'-DNA terminus at the T position. The sequence GATG is more frequent in the non transcribed strand of the early and late transcription of SV40 than in the transcribed strands. This finding is consistent with the role of topoisomerase I in transcription.
喜树碱是一种抗肿瘤药物，是真核生物拓扑异构酶I的特异性抑制剂。酶抑制作用与拓扑异构酶I和DNA之间可裂解复合物的稳定有关。在SV40基因组中确定了喜树碱产生的L1210拓扑异构酶I介导的DNA断裂的基因组和DNA序列定位。DNA切割主要是单链的，且定位在DNA的选择性区域。在早期转录区域的编码链上的核苷酸4995处发现了一个主要切割位点。确定了显著切割位点（两个72 bp重复序列中的核苷酸127和199以及核苷酸4955）的DNA序列。在SV40 DNA中发现了一个DNA共有序列5'-GATG-3'。切割发生在T和G之间，拓扑异构酶I与T位置的3'-DNA末端相连。序列GATG在SV40早期和晚期转录的非转录链中比在转录链中更频繁。这一发现与拓扑异构酶I在转录中的作用一致。
