Mikek Clinton G, West Savannah J, Gwin J Cole, Dayal Neetu, Sintim Herman O, Lewis Edwin A
Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States.
Center for Drug Discovery, Purdue University, 720 Clinic Drive, West Lafayette, Indiana 47907, United States.
ACS Omega. 2018 Sep 30;3(9):11582-11591. doi: 10.1021/acsomega.8b01621. Epub 2018 Sep 21.
Diminazene, DMZ, (or berenil) has been reported as a tight binder of G-quadruplexes. G-Quadruplex structures are often located in the promotor regions of oncogenes and may play a regulatory role in gene expression based on the stability of the folding topology. In this study, attempts have been made to characterize the specificity of DMZ binding toward multiple G-quadruplex topologies or foldamers. Mutant sequences of the G-quadruplex forming promotor regions of several oncogenes were designed to exhibit restricted loop lengths and folding topologies. Circular dichroism was used to confirm the quadruplex topology of mutant BCL2, KRAS, and c-MYC sequences, human telomere (Na and K) G-quadruplexes and their complexes with DMZ and analogs thereof. Isothermal titration calorimetry was used to generate a complete thermodynamic profile (Δ, Δ, -Δ) for the formation of DMZ and analog complexes with the target G-quadruplexes. DMZ binds to parallel and/or mixed parallel/antiparallel quadruplex DNA motifs with stoichiometries up to 8:1 and via three binding modes with varying affinities. In the case of the parallel G-quadruplexes, with the exception of the long-looped c-MYC mutant, the highest affinity binding event (mode 1) is driven by enthalpy. DMZ binding to the long-looped c-MYC mutant exhibits a very favorable entropy change in addition to a moderately favorable enthalpy change. Mode 1 binding to the antiparallel and mixed parallel/antiparallel hTel quadruplexes is also driven by favorable enthalpy changes. In all cases, the intermediate DMZ affinity binding (mode 2) is driven almost entirely by entropy, with small or unfavorable enthalpic contributions. The weakest binding event (mode 3) is also entropically driven with small or moderate enthalpic contributions.
据报道，二脒那秦（DMZ，或贝尼尔）是一种与G-四链体紧密结合的物质。G-四链体结构通常位于癌基因的启动子区域，基于折叠拓扑结构的稳定性，可能在基因表达中发挥调节作用。在本研究中，已尝试表征DMZ对多种G-四链体拓扑结构或折叠体的结合特异性。设计了几种癌基因的G-四链体形成启动子区域的突变序列，以呈现受限的环长度和折叠拓扑结构。利用圆二色性来确认突变型BCL2、KRAS和c-MYC序列、人端粒（Na和K）G-四链体及其与DMZ及其类似物的复合物的四链体拓扑结构。等温滴定量热法用于生成DMZ及其类似物与目标G-四链体形成复合物的完整热力学图谱（ΔH、ΔS、-ΔG）。DMZ以高达8:1的化学计量比并通过三种具有不同亲和力的结合模式与平行和/或混合平行/反平行四链体DNA基序结合。在平行G-四链体的情况下，除了长环c-MYC突变体之外，最高亲和力的结合事件（模式1）由焓驱动。DMZ与长环c-MYC突变体的结合除了适度有利的焓变外，还表现出非常有利的熵变。模式1与反平行和混合平行/反平行hTel四链体的结合也由有利的焓变驱动。在所有情况下，中等DMZ亲和力的结合（模式2）几乎完全由熵驱动，焓的贡献很小或不利。最弱的结合事件（模式3）也是由熵驱动，焓的贡献很小或中等。
