Target identification of a macrocyclic hexaoxazole G-quadruplex ligand using post-target-binding visualization

• Published in: Chemical communications (Cambridge, England) Vol. 56; no. 85; pp. 1295 - 1298
• Main Authors: Yasuda, Mizuho, Ma, Yue, Okabe, Sachiko, Wakabayashi, Yuki, Su, Dongdong, Chang, Young-Tae, Seimiya, Hiroyuki, Tera, Masayuki, Nagasawa, Kazuo
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 04.11.2020
• Subjects: Alkynes; Anticancer properties; antineoplastic activity; azides; Binding; Binding Sites; Biological activity; Biological properties; Carbon monoxide; Cell Line, Tumor; cytotoxicity; fluorescent dyes; G-Quadruplexes; Humans; Ligands; Macrocyclic Compounds - chemistry; moieties; Molecular Structure; Oxazoles - chemistry; RNA; Target recognition; Toxicity; Visualization
• ISSN: 1359-7345; 1364-548X; 1364-548X
• DOI: 10.1039/d0cc04957c

Macrocyclic hexaoxazoles (6OTDs) are G-quadruplex (G4) ligands, and some derivatives, such as L2H2-6OTD ( 1a ) bearing two aminobutyl side chains, show cytotoxicity towards cancer cells. To identify the cellular target of 1a , we employed a post-target-binding strategy utilizing click reaction (Huisgen cyclization) between the azide-conjugated ligand L2H2-6OTD-Az ( 1b ) and the cell-permeable dye CO-1 bearing a strained alkyne moiety and the BODIPY fluorophore under Cu-free conditions. We confirmed that introduction of the small azide group did not alter the physical or biological properties, including anti-cancer activity, of 1a , and we also demonstrated bias-free localization of CO-1. The post-binding visualization strategy suggested that L2H2-6OTD ( 1a ) colocalized with RNA G4 in living cells. Macrocyclic hexaoxazoles (6OTD) are G-quadruplex (G4) ligands. The azide-modified derivative L2H2-6OTD-Az shows cytotoxicity towards cancer cells and visualizes G4 in live cells together with BODIPY bearing a strained-alkyne (CO-1).