Woynarowski J M, McHugh M, Sigmund R D, Beerman T A
Grace Cancer Drug Center, Roswell Park Memorial Institute, Buffalo, New York 14263.
Mol Pharmacol. 1989 Feb;35(2):177-82.
The effects of distamycin, Hoechst 33258, and 4',6-diamidine-2-phenylindole (DAPI) on the catalytic activity of topoisomerase II from L1210 cells were determined. These compounds were used as model agents capable of AT-specific binding in the minor groove of DNA while producing no profound long-range alterations to the DNA structure. Two types of reactions catalyzed by topoisomerase II were examined, relaxation of supercoiled DNA and decatenation of highly catenated DNA. Distamycin at low concentrations (0.2-2 microM) substantially stimulated relaxation of supercoiled pBR322 DNA. Higher drug levels (25-50 microM) resulted in a potent inhibition of relaxation. At the stimulatory concentrations of distamycin, only completely relaxed reaction products were observed, as in the absence of the drug. The onset of inhibition (caused by 5-10 microM distamycin) was accompanied by the appearance of partially relaxed intermediates. Similar inhibition of relaxation was observed for Hoechst 33258 and DAPI but, unlike distamycin, these agents produced only marginal stimulation of relaxation when added in low noninhibitory concentrations. Another reaction of topoisomerase II, decatenation of catenated kinetoplast DNA, was also inhibited by distamycin, Hoechst 33258, and DAPI at concentrations similar to those inhibiting the relaxation reaction. This study demonstrates that agents binding to the minor groove of DNA represent a new class of drugs interfering with topoisomerase II and provides possibilities for modulation of this important enzyme.
测定了偏端霉素、Hoechst 33258和4',6-二脒基-2-苯基吲哚（DAPI）对L1210细胞拓扑异构酶II催化活性的影响。这些化合物用作能够在DNA小沟中特异性结合AT，同时不会对DNA结构产生深远的长程改变的模型试剂。研究了拓扑异构酶II催化的两种反应，超螺旋DNA的松弛和高度连环化DNA的解连环。低浓度（0.2 - 2 microM）的偏端霉素能显著刺激超螺旋pBR322 DNA的松弛。较高的药物浓度（25 - 50 microM）会导致对松弛的有效抑制。在偏端霉素的刺激浓度下，如在无药物时一样，仅观察到完全松弛的反应产物。抑制的起始（由5 - 10 microM偏端霉素引起）伴随着部分松弛中间体的出现。对Hoechst 33258和DAPI也观察到类似的松弛抑制，但与偏端霉素不同，当以低的非抑制浓度添加时，这些试剂仅产生轻微的松弛刺激。拓扑异构酶II的另一个反应，即连环化动质体DNA的解连环，也受到偏端霉素、Hoechst 33258和DAPI的抑制，其浓度与抑制松弛反应的浓度相似。这项研究表明，与DNA小沟结合的试剂代表了一类干扰拓扑异构酶II的新型药物，并为调节这种重要酶提供了可能性。
