Investigation of the ligand topology for targeting multimeric G-quadruplex DNA Ariadna Gil Martínez, Laura Mulet-Rivero, Andrea Lázaro-Gómez, Isabel Pont, Cristina Galiana-Rosellò, Enrique García-España, Jorge González-García University of Valencia,Spain DNA can adopt a variety of conformations besides the famous double helical structure B-DNA, such as triplexes, i- motifs, three/four-way junctions or G-quadruplexes (G4s). The latter one is a supramolecular assembly of two or more tetrads, which arise from the hydrogen bonding network of four coplanar guanines. The stability and topology of G4 structures are mainly controlled by the alkali metal cation employed, the base sequence and the nature of the nucleic acid (DNA or RNA). Strikingly, a large number of putative G-quadruplex forming sequences have been identified in the genomes of human, microorganisms and viruses, and evidence suggest their pivotal role in key biological processes.[1] In particular, telomeres are guanine-rich regions with putative G4-forming DNA sequences and have been associated with ageing and cancer. Therefore, G4 structures are currently tested as a therapeutic target to inhibit telomere elongation in cancer cells.[2] Telomere sequences comprise hundreds of TTAGGG repeats which form a superstructure constituted by multiple G4s, termed multimeric G4s (multG4s). It is noteworthy that from the vast human genome, telomeric DNA comprises one of the very few regions able to fold into multG4s. Herein, we present our synthetic efforts to develop new organic molecules [3] able to interact with multG4s. We have prepared a family of linear, macrocyclic and cryptand ligands taking into account the first generation of G4 binders with triphenylamine moieties.[3] Our initial assessment on the binding abilities of the ligands has been conducted by FRET melting, fluorimetric and electrophoretic mobility shift assay. The results of the stabilisation effect on multG4s, monomeric G4s and duplexes indicate the strong stabilisation effect of the cryptand-like ligands of multimeric G-quadruplexes together with a preference for multG4s over monomeric G4s and the double-helical DNA structure. Altogether, the analysis of the melting variations highlights the importance of the molecule net charge and the reinforced structure of the ligands to bind strongly multimeric G4s.[4] Currently, we are exploring the application of these ligands as anticancer drugs by targeting the multimeric G4 structures formed in the telomeric regions of cancer cells. References 1. D. Rhodes, H. J. Lipps, Nucleic Acids Res., 2015 , 43 , 8627-8637. 2. S. Neidle, S. Balasubramanian in Quadruplex Nucleic Acids , RSC: Cambridge, 2006 . N. Kosiol et al. , Mol. Cancer , 2021 , 20(1) , 40. 3. I. Pont et al. , Chem. Eur. J. , 2018 , 24 ,10850 –10858; ChemBioChem , 2020 , 21 ,1167 –1177; Metode, 2021 , 2174-9221. 4. A. Gil-Martinez et al. , in preparation.
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