Disordering of Human Telomeric G-Quadruplex with Novel Antiproliferative Anthrathiophenedione

Linear heteroareneanthracenediones have been shown to interfere with DNA functions, thereby causing death of human tumor cells and their drug resistant counterparts. Here we report the interaction of our novel antiproliferative agent 4,11-bis[(2-{[acetimido]amino}ethyl)amino]anthra[2,3-b]thiophene-5,10-dione with telomeric DNA structures studied by isothermal titration calorimetry, circular dichroism and UV absorption spectroscopy. New compound demonstrated a high affinity (Kass∼106 M−1) for human telomeric antiparallel quadruplex d(TTAGGG)4 and duplex d(TTAGGG)4∶d(CCCTAA)4. Importantly, a ∼100-fold higher affinity was determined for the ligand binding to an unordered oligonucleotide d(TTAGGG TTAGAG TTAGGG TTAGGG unable to form quadruplex structures. Moreover, in the presence of Na+ the compound caused dramatic conformational perturbation of the telomeric G-quadruplex, namely, almost complete disordering of G-quartets. Disorganization of a portion of G-quartets in the presence of K+ was also detected. Molecular dynamics simulations were performed to illustrate how the binding of one molecule of the ligand might disrupt the G-quartet adjacent to the diagonal loop of telomeric G-quadruplex. Our results provide evidence for a non-trivial mode of alteration of G-quadruplex structure by tentative antiproliferative drugs.

线性杂芳蒽二酮已被证实可干扰DNA功能，进而导致人类肿瘤细胞及其耐药株死亡。本文报道了新型抗增殖剂4,11-双[(2-{[乙酰亚胺基]氨基}乙基)氨基]蒽并[2,3-b]噻吩-5,10-二酮与端粒DNA结构的相互作用，研究采用了等温滴定量热法（isothermal titration calorimetry）、圆二色光谱法（circular dichroism）以及紫外吸收光谱法（UV absorption spectroscopy）。该化合物对人类端粒反平行G-四链体d(TTAGGG)4与双链体d(TTAGGG)4∶d(CCCTAA)4展现出较高的结合亲和力（结合常数Kass≈10⁶ M⁻¹）。值得注意的是，该配体与无法形成G-四链体结构的无序寡核苷酸d(TTAGGG TTAGAG TTAGGG TTAGGG)的结合亲和力竟高出约100倍。此外，在钠离子存在的条件下，该化合物会对端粒G-四链体造成显著的构象扰动，即G-四分体几乎完全解聚；而在钾离子存在时，同样可检测到部分G-四分体的解聚现象。研究通过分子动力学模拟（molecular dynamics simulations）阐释了单分子配体结合如何破坏端粒G-四链体对角环旁侧的G-四分体。本研究结果为潜在抗增殖药物通过一种非平凡的作用模式改变G-四链体结构提供了实验依据。