Interaction of clinically important human DNA topoisomerase I poison, topotecan, with double‐stranded DNA

Abstract

Topotecan (TPT), a water-soluble derivative of camptothecin, is a potent antitumor poison of human DNA topoisomerase I (top1) that stabilizes the cleavage complex between the enzyme and DNA. The role of the recently discovered TPT affinity to DNA remains to be defined. The aim of this work is to clarify the molecular mechanisms of the TPT-DNA interaction and to propose the models of TPT-DNA complexes in solution in the absence of top1. It is shown that TPT molecules form dimers with a dimerization constant of (4.0 +/- 0.7) x 10(3) M(-1) and the presence of DNA provokes more than a 400-fold increase of the effective dimerization constant. Flow linear dichroism spectroscopy accompanied by circular dichroism, fluorescence, and surface-enhanced Raman scattering experiments provide evidence that TPT dimers are able to bind DNA by bridging different DNA molecules or distant DNA structural domains. This effect may provoke modification of the intrinsic geometry of the cruciform DNA structures, leading to the appearance of new crossover points that serve as the sites of the top1 loading position. The data presume the hypothesis of TPT-mediated modulation of top1-DNA recognition before ternary complex formation.

Multiple Binding Modes of the Camptothecin Family to DNA Oligomers

“…[14] However, our studies suggest that the interaction is one of stacking against a base pair rather than an interaction with the minor groove. [11] An issue that should be addressed in drug-DNA interactions is the possibility of spin diffusion as a source of indirect cross-peaks. [15] A good indicator of spin diffusion is the presence of multiple cross-peaks involving a network of adjacent nuclei, and these are not observed.…”

“…[11] DNA/TPT binding constant measurements: The binding constant of TPT to DNA was measured by UV, by use of equations corrected for TPT self-association as described in the Experimental Section. The binding constant of TPT with d(GCGATCGC) 2 was obtained as K a = 2.5 mm…”

Binding of topotecan to chromatin: Insights into cooperative binding and comparison with DNA

“…Although, direct interaction of TPT with DNA has been the subject of several reports [11,12,28], no work has been published on the effect of this drug on DNA-histone complex in chromatin structure. Therefore the goal of this study was to define binding affinity of TPT to chromatin compared to DNA to elucidate the mechanism of TPT action at the chromatin level and illustrate the possible role of histone proteins in this binding process.…”

“…Raman spectroscopy has revealed direct interaction of TPT with dG through H-bonds formation between the TPT D and E rings and dG within the TPT-DNA complexes [9,10]. Moreover, TPT is able to form dimers in aqueous solution and its content is increased in the presence of double-stranded DNA representing possible crosslinking of two distinct DNA molecules in solution [11,12]. Topotecan mediates topoisomerase I activity at a unique DNA sequences, inhibits autophagy in colon cancer cells and is highly germ cell mutagen [13][14][15].…”

Identification and characterization of pharmaceuticals using Raman and surface‐enhanced Raman scattering

“…Many other molecular compounds with different pharmacological activity have been analysed using Raman and SERS techniques, including the antihypertensive 1,4-dihydrazinophtalazine sulfate, 80 the antimicrobial agent rivanol, 81 chiralˇ-blockers, 12 antiretrovirals, 82 narcotics, 83 -85 antitumour agents (6-mercaptopurine 86 , 9-phenyl-and 9-aminoacridine, 87 -88 camptothecin 89 and its water-soluble derivative topotecan 90 ) and HIV inhibitors (betulinic acid). 91 …”