Takahashi Shuntaro, Bhowmik Sudipta, Sato Shinobu, Takenaka Shigeori, Sugimoto Naoki
FIBER (Frontier Institute for Biomolecular Engineering Research), Konan University, Kobe 650-0047, Japan.
Department of Biophysics, Molecular Biology & Bioinformatics, University of Calcutta, Kolkata 700009, India.
Life (Basel). 2022 Apr 7;12(4):553. doi: 10.3390/life12040553.
The human telomere region is known to contain guanine-rich repeats and form a guanine-quadruplex (G4) structure. As telomeres play a role in the regulation of cancer progression, ligands that specifically bind and stabilize G4 have potential therapeutic applications. However, as the human telomere sequence can form G4 with various topologies due to direct interaction by ligands and indirect interaction by the solution environment, it is of great interest to study the topology-dependent control of replication by ligands. In the present study, a DNA replication assay of a template with a human telomere G4 sequence in the presence of various ligands was performed. Cyclic naphthalene diimides (cNDI1 and cNDI2) efficiently increased the replication stall of the template DNA at G4 with an anti-parallel topology. This inhibition was stability-dependent and topology-selective, as the replication of templates with hybrid or parallel G4 structures was not affected by the cNDI and cNDI2. Moreover, the G4 ligand fisetin repressed replication with selectivity for anti-parallel and hybrid G4 structures without stabilization. Finally, the method used, referred to as quantitative study of topology-dependent replication (QSTR), was adopted to evaluate the correlation between the replication kinetics and the stability of G4. Compared to previous results obtained using a modified human telomere sequence, the relationship between the stability of G4 and the effect on the topology-dependent replication varied. Our results suggest that native human telomere G4 is more flexible than the modified sequence for interacting with ligands. These findings indicate that the modification of the human telomeric sequence forces G4 to rigidly form a specific structure of G4, which can restrict the change in topology-dependent replication by some ligands.
已知人类端粒区域含有富含鸟嘌呤的重复序列，并能形成鸟嘌呤四链体（G4）结构。由于端粒在癌症进展调控中发挥作用，特异性结合并稳定G4的配体具有潜在的治疗应用价值。然而，由于人类端粒序列可因配体的直接相互作用和溶液环境的间接相互作用而形成具有多种拓扑结构的G4，因此研究配体对复制的拓扑依赖性控制具有重要意义。在本研究中，我们在存在各种配体的情况下，对具有人类端粒G4序列的模板进行了DNA复制测定。环状萘二亚胺（cNDI1和cNDI2）有效地增加了具有反平行拓扑结构的G4处模板DNA的复制停滞。这种抑制作用依赖于稳定性且具有拓扑选择性，因为具有杂交或平行G4结构的模板复制不受cNDI1和cNDI2的影响。此外，G4配体漆黄素对反平行和杂交G4结构具有选择性抑制复制的作用，但并不具有稳定作用。最后，我们采用了称为拓扑依赖性复制定量研究（QSTR）的方法来评估复制动力学与G4稳定性之间的相关性。与先前使用修饰后的人类端粒序列获得的结果相比，G4稳定性与拓扑依赖性复制效应之间的关系有所不同。我们的结果表明，天然人类端粒G4在与配体相互作用方面比修饰后的序列更具灵活性。这些发现表明，人类端粒序列的修饰迫使G4刚性地形成特定的G4结构，这可能会限制某些配体对拓扑依赖性复制的改变。
