人端粒G-四链体DNA与百里醌的相互作用：百里醌抗癌作用的一种可能机制。

Interaction of human telomeric G-quadruplex DNA with thymoquinone: a possible mechanism for thymoquinone anticancer effect.

作者信息

Salem Alaa A, El Haty Ismail A, Abdou Ibrahim M, Mu Yuguang

机构信息

Department of Chemistry, College of Science, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates.

出版信息

Biochim Biophys Acta. 2015 Feb;1850(2):329-42. doi: 10.1016/j.bbagen.2014.10.018. Epub 2014 Oct 24.

DOI:10.1016/j.bbagen.2014.10.018

PMID:25450185

Abstract

BACKGROUND

Thymoquinone (TQ) has been documented to possess chemo-preventive and chemotherapeutic antitumor effects. Studies reported that TQ inhibits the growth of cancer cells in animal models, culture and xenografted tumors. Molecular mechanisms underlying these anticancer effects were attributed to inductions of cell cycle arrest, apoptosis, oxidative damage of cellular macromolecules, blockade of tumor angiogenesis and inhibitions in migration, invasion and metastasis of cancer cells. On the other hand, human telomere DNA plays a role in regulating genes' transcriptions. It folds up into G-quadruplex structures that inhibit telomerase enzyme over-expressed in cancerous cells. Molecules that selectively stabilize G-quadruplex are potential anticancer agents. Therefore, this work aimed to explore the interaction of TQ with G-quadruplex DNA as a possible underlying mechanism for the anticancer effect of TQ.

METHODS

Interactions of TQ with telomeric G-quadruplex (5'-AGGG(TTAGGG)3-3') and duplex DNAs were studied using UV-vis, fluorescence, circular dichroism, liquid and solid NMR (1H and 13C), melting temperature and docking simulation.

RESULTS

Changes in UV-vis, CD, fluorescence, 1H NMR and 13C NMR, spectra as well as melting temperatures and docking simulations provided evidences for TQ's interactions with G-quadruplex. TQ was found to interact with G-quadruplex on two binding sites adjacent to the TTA loop with binding constants 1.80×10(5) and 1.12×10(7) M(-1). Melting temperatures indicated that TQ stabilized G-quadruplex by 5.6 °C and destabilized ct-DNA by 5.1 °C. Selectivity experiment indicated that TQ is preferentially binding to G-quadruplex over duplex with selectivity coefficients of 2.80-3.33×10(-3). Results suggested an intercalation binding mode based on π-π stacking.

CONCLUSION

Our results propose that TQ can possibly act as a G-quadruplex DNA stabilizer and subsequently contribute to the inhibition of telomerase enzyme and cancer's proliferation.

GENERAL SIGNIFICANCE

Our results represent a change in the paradigms reported for structural features of G-quadruplex's stabilizers and anticancer mechanisms of TQ.

摘要

背景

已证明百里醌（TQ）具有化学预防和化疗抗肿瘤作用。研究报道，TQ在动物模型、细胞培养和异种移植肿瘤中可抑制癌细胞生长。这些抗癌作用的分子机制归因于诱导细胞周期停滞、凋亡、细胞大分子的氧化损伤、阻断肿瘤血管生成以及抑制癌细胞的迁移、侵袭和转移。另一方面，人类端粒DNA在调节基因转录中起作用。它折叠成G-四链体结构，可抑制癌细胞中过度表达的端粒酶。选择性稳定G-四链体的分子是潜在的抗癌剂。因此，本研究旨在探索TQ与G-四链体DNA的相互作用，作为TQ抗癌作用的一种可能潜在机制。

方法

采用紫外可见光谱、荧光光谱、圆二色光谱、液体和固体核磁共振（1H和13C）、熔解温度和对接模拟等方法研究TQ与端粒G-四链体（5'-AGGG(TTAGGG)3-3'）和双链DNA的相互作用。

结果

紫外可见光谱、圆二色光谱、荧光光谱、1H核磁共振和13C核磁共振光谱的变化以及熔解温度和对接模拟结果为TQ与G-四链体的相互作用提供了证据。发现TQ在与TTA环相邻的两个结合位点与G-四链体相互作用，结合常数分别为1.80×10(5)和1.12×10(7) M(-1)。熔解温度表明，TQ使G-四链体稳定5.6℃，使双链DNA不稳定5.1℃。选择性实验表明，TQ优先与G-四链体结合，而不是双链DNA，选择性系数为2.80-3.33×10(-３)。结果表明其结合模式为基于π-π堆积的插入结合。