Funding (ICMUB):
Duration: Oct. 25 – 48 mois
Scientific leader ICMUB: David Monchaud
Summary
G-quadruplexes (G4s) are non-B secondary DNA structures that fold from G-rich sequences. These structures can be targeted by specific small molecules, called G4 ligands. Several families of G4 ligands have been identified and, while they share a similar ability to interact with G4s in vitro, they display different activities in cells including for some a cytotoxic activity. Based on these various and valuable cellular activities, many applications have been proposed for G4 ligands, including as treatments against cancers, viral infections, parasites but also in the context of neurodegenerative diseases. However, being able to exploit this class of molecules to treat diseases with minimal side effects first requires to fully understand how they mediate their effects, to ultimately be able to harness them.
Recently, thanks to an unbiased approach, we discovered that the cytotoxic activity of two G4 ligands, including the widely used pyridostatin (PDS), results from DNA topoisomerase 2 alpha (TOP2A) poisoning at G4 sites. However, we also established that other cytotoxic G4 ligands, including a closely related PDS analogue, do not poison TOP2s, which implies that subtle structural features are sufficient to modify this property. The TOP2-G4 project aims at classifying the prototype G4 ligands, at deciphering at the biochemical and structural level how some G4 ligands poison TOP2A, while others do not, and, in that instance, at identifying the mechanisms underlying their cytotoxic effect.
This ambitious project relies on the complementary expertise of three groups: the Britton’s lab at IPBS for biology and original functional genomics approaches to identify small molecule mechanism of action, the Lamour’s lab at IGBMC for biochemical and structural characterization through cutting edge techniques including cryoEM and the Monchaud’s lab at ICMUB for synthesis and biophysical evaluation of novel G4 ligands, including functionalized ones. Together, we will 1/ perform a side-by-side evaluation of prototype G4 ligands, 2/ determine how the cytotoxic non-TOP2A poisoning ligands mediate their effect, and 3/ establish the molecular basis underlying the TOP2A poisoning ability of G4 ligands through biochemical, structural and mutational studies. From these deep insights, novel ligands will be synthesized to show in a proof-of-concept study that their properties can be fully controlled. Related pairs of functionalized ligands (TOP2 poisoning and non-poisoning) will also be generated, validated and used to analyze their differential localization and protein partners, which will shed light on the cellular mechanisms that translate specific ligand features into specific biological properties.
Altogether this project will allow to fully understand the biological effects of G4 ligands and show how they can be controlled, which will unlock and extend their future therapeutic applications to human diseases in which G4s have been demonstrated to be involved.
Partners:
- Sébastien Britton, IPBS Toulouse FR
- Valérie Lamour, IGBMC Strasbourg, FR