Identification et caractérisation de ligands des quadruplexes de guanines: cibler les télomères et/ou la télomérase?

Abstract : Guanine quadruplexes (G4) are non-canonical nucleic acids structures formed by guanine-rich DNA and RNA sequences. In vivo, such structures appear to be implicated in genome dynamics, and especially at telomeres. In the latter case, G4 folding at telomeres using ligands stabilizing these structures could limit the proliferation of cancer cells. During this thesis work, we developed a middle-throughput method allowing to test the effect of various molecules on the stabilization of the human telomeric G4. This method is based on thermal dissociation of G4 followed by FRET, in the presence of several DNA competitive structures. It allowed us to identify some series of ligands displaying interesting affinity and selectivity for G4-DNA, such as neomycin-capped macrocycles and N-methylbisquinolinium phenanthrolin derivatives. We then characterized more thoroughly the molecular mechanisms by which these ligands could stabilize G4 structures. A kinetic study using a model of tetramolecular G4 showed that some peculiar G4 ligand families were able to strongly increase the association rate of the G4. We also analyzed telomerase inhibition in presence of these ligands. Using a direct primer extension assay, we highlighted that only few ligands were able to interfere with the telomerase processive elongation on a DNA substrate which did not form an intramolecular G4 initially. These results contributes to the already growing suspicion that cellular effects of these ligands are not solely related to their effect on telomerase, but should also result from their effect on other telomeric proteins essential to maintain of functional telomeres. Finally, we investigated the possibility to transpose the strategy of targeting telomeres with G4 ligands to limit cellular proliferation, to the pathogen organism responsible for Malaria : Plasmodium falciparum. We showed the existence of a 3' telomeric overhang in the parasite an its potential folding into a G4 structure under physiological conditions. We identified several molecules stabilizing the parasite telomeric G4 with a good selectivity versus duplex DNA, and we tested these drugs on the parasite proliferation.
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Contributor : Anne de Cian <>
Submitted on : Friday, December 11, 2009 - 7:40:41 PM
Last modification on : Thursday, February 7, 2019 - 1:33:16 AM
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  • HAL Id : tel-00440832, version 1

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Anne de Cian. Identification et caractérisation de ligands des quadruplexes de guanines: cibler les télomères et/ou la télomérase?. Biochimie [q-bio.BM]. Université Pierre et Marie Curie - Paris VI, 2007. Français. ⟨tel-00440832⟩

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