Issue 21, 2023

Probing juxtaposed G-quadruplex and hairpin motifs using a responsive nucleoside probe: a unique scaffold for chemotherapy

Abstract

Paucity of efficient probes and small molecule ligands that can distinguish different G-quadruplex (GQ) topologies poses challenges not only in understanding their basic structure but also in targeting an individual GQ form from others. Alternatively, G-rich sequences that harbour unique chimeric structural motifs (e.g., GQ-duplex or GQ-hairpin junctions) are perceived as new therapeutic hotspots. In this context, the epidermal growth factor receptor (EGFR) gene, implicated in many cancers, contains a 30 nucleotide G-rich segment in the promoter region, which adopts in vitro two unique architectures each composed of a GQ topology (parallel and hybrid-type) juxtaposed with a hairpin domain. Here, we report the use of a novel dual-app probe, C5-trifluoromethyl benzofuran-modified 2′-deoxyuridine (TFBF-dU), in the systematic analysis of EGFR GQs and their interaction with small molecules by fluorescence and 19F NMR techniques. Notably, distinct fluorescence and 19F NMR signals exhibited by the probe enabled the quantification of the relative population of random, parallel and hybrid-type GQ structures under different conditions, which could not be obtained by conventional CD and 1H NMR techniques. Using the fluorescence component, we quantified ligand binding properties of GQs, whereas the 19F label enabled the assessment of ligand-induced changes in GQ dynamics. Studies also revealed that mutations in the hairpin domain affected GQ formation and stability, which was further functionally verified in polymerase stop assay. We anticipate that these findings and useful properties of the nucleoside probe could be utilized in designing and evaluating binders that jointly target both GQ and hairpin domains for enhanced selectivity and druggability.

Graphical abstract: Probing juxtaposed G-quadruplex and hairpin motifs using a responsive nucleoside probe: a unique scaffold for chemotherapy

Supplementary files

Article information

Article type
Edge Article
Submitted
30 jan 2023
Accepted
30 apr 2023
First published
02 maj 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 5627-5637

Probing juxtaposed G-quadruplex and hairpin motifs using a responsive nucleoside probe: a unique scaffold for chemotherapy

S. Y. Khatik, S. Sudhakar, S. Mishra, J. Kalia, P. I. Pradeepkumar and S. G. Srivatsan, Chem. Sci., 2023, 14, 5627 DOI: 10.1039/D3SC00519D

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