Molecular Recognition and Imaging of Human Telomeric G-Quadruplex DNA in Live Cells: A Systematic Advancement of Thiazole Orange Scaffold To Enhance Binding Specificity and Inhibition of Gene Expression

Abstract

A series of fluorescent ligands, which were systematically constructed from thiazole orange scaffold, was investigated for their interactions with G-quadruplex structures and antitumor activity. Among the ligands, compound 3 was identified to exhibit excellent specificity toward telomere G4-DNA over other nucleic acids. The affinity of 3-Htg24 was almost 5 times higher than that of double-stranded DNA and promoter G4-DNA. Interaction studies showed that 3 may bind to both G-tetrad and the lateral loop near the 5′-end. The intracellular colocalization with BG4 and competition studies with BRACO19 reveal that 3 may interact with G4-structures. Moreover, 3 reduces the telomere length and downregulates hTERC and hTERT mRNA expression in HeLa cells. The cytotoxicity of 3 against cancer cells (IC50 = 12.7–16.2 μM) was found to be generally higher than noncancer cells (IC50 = 52.3 μM). The findings may support that the ligand is telomere G4-DNA specific and may provide meaningful insights for anticancer drug design.

Structurally diverse G-quadruplexes as the noncanonical nucleic acid drug target for live cell imaging and antibacterial study

“…We found that, apart from adopting a planar core molecular fragment to construct G4-ligands, the overall molecular size, 116 symmetry, 117,118 flexibility, 83 and the character of terminal groups 119–122 may affect the in vitro selectivity of the ligand toward G4-structures against RNA, single- and double-stranded DNA. Our study suggests that some small-sized molecular scaffolds including benzothiazole-benzofuroquinolinium, 123,124 benzothiazole-indolium, 125 1-methylquinolinium, 126 thiazole orange 81,84,127 and benzo[ e ]indole 128 are good molecular fragments for the design of fluorescent G4-ligands to achieve high discrimination ability, sensitivity and quantum yield targeting certain types of G4s for in vitro sensing and live cell imaging. In the design of G4-ligands, the molecular symmetry of G4-ligands has been rarely discussed in the literature.…”

Engineering a Red Fluorescent Protein Chromophore for Visualization of RNA G-Quadruplexes

“…Over the past decades, intense research has focused on developing small-molecule fluorescent probes for monitoring G4s in cells, offering means to the relevant investigations of G4 structures and function in cellular studies. − Although some G4-binding dyes have been developed, there are still limitations, such as the inability to visualize nuclear RNA G4s and relatively low signal-to-noise ratios. In this regard, a commercial benzothiazole dye thioflavin T (ThT) exhibits high selectivity and binding affinity toward G4 structures and directly visualizes the RNA G4s in cell nuclei. , By modulating the structure of molecules, an increasing number of ThT analogues have been engineered, which are applied in the real-time imaging of DNA G4 and viral RNA G4.…”

Structured Waters Mediate Small Molecule Binding to G-Quadruplex Nucleic Acids

“…GQ-forming sequences have been found in the genomes of many organisms, ranging from viruses [23][24][25][26][27] to bacteria [28][29][30][31] and malaria [32][33][34]. GQs have been visualized in fixed [35][36][37][38] and in live cells [39][40][41][42], where their existence may be more than transient, with several roles in gene function [3,4,12]; for example, GQ folding is associated with sites of active transcription and precedes transcription itself [13,22].…”