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Updated: Jan 11, 2026
Single-Molecule Fluorescence Visualization of DNA Polymerase Dynamics at G-Quadruplexes
Published on: April 4, 2025
Evidence that G-quadruplexes form in pathogenic fungi and represent promising antifungal targets
Georgie Middleton1,2, Fuad O Mahamud3, Isabelle S R Storer1,2
1School of Chemistry, Pharmacy and Pharmacology, University of East Anglia, Norwich, NR4 7TJ, UK.
Abstract:
Fungi are estimated to cause the death of almost 4 million people annually, and we urgently need new drug targets to overcome antifungal resistance. We found that four-stranded nucleic acid structures called G-quadruplexes (G4s) could form within the critical priority fungal pathogen Aspergillus fumigatus. Sequences with the potential to form G4s could be found in genes involved in fungal growth, virulence, and drug resistance. This included cyp51A, which encodes the target of azoles. Notably, we observed the formation of both canonical and unusual acid-stabilised G4s in these sequences. We found that PhenDC3 (a G4-stabilising ligand) could refold DNA into antiparallel G4 structures in cyp51A that were associated with decreased transcription. PhenDC3 also had potent fungistatic activity, prevented germination, synergised with the antifungal amphotericin B in vitro and in vivo, and displayed low genotoxicity and cytotoxicity towards human cells. Interestingly, PhenDC3 had greater antifungal activity towards the pan-azole-resistant A. fumigatus TR34/L98H isolate, and another G4-stabiliser, pyridostatin, killed multi-drug-resistant Candida auris. Taken together, G4s represent a promising target for the development of antifungals with novel mechanisms of action.
Insights
New antifungals are needed to combat drug resistance. This study identifies G-quadruplexes (G4s) in Aspergillus fumigatus as potential drug targets, with a compound showing potent antifungal activity and low toxicity.
Area of Science:
- Mycology
- Molecular Biology
- Drug Discovery
Background:
- Fungal infections cause millions of deaths annually, necessitating novel antifungal drug targets due to rising resistance.
- Antifungal resistance is a significant global health threat, particularly in pathogenic fungi like Aspergillus fumigatus.
Purpose of the Study:
- To investigate the potential of G-quadruplex (G4) structures as novel targets for antifungal drug development.
- To evaluate the antifungal efficacy and safety of G4-stabilizing ligands against key fungal pathogens.
Main Methods:
- Bioinformatic analysis to identify G4-forming sequences in Aspergillus fumigatus genes.
- In vitro experiments using G4-stabilizing ligands (PhenDC3, pyridostatin) to assess effects on fungal growth, transcription, and drug synergy.
- In vivo efficacy and toxicity studies in relevant models.
Main Results:
- G-quadruplex (G4) forming sequences were identified in essential Aspergillus fumigatus genes, including cyp51A, crucial for azole antifungal targets.
- PhenDC3 demonstrated potent fungistatic activity, inhibited fungal germination, and synergized with amphotericin B, showing low human cell toxicity.
- PhenDC3 exhibited enhanced activity against azole-resistant Aspergillus fumigatus, and pyridostatin showed efficacy against multi-drug-resistant Candida auris.
Conclusions:
- G-quadruplexes (G4s) represent a promising novel target class for developing urgently needed antifungals.
- G4-stabilizing ligands offer a potential strategy to overcome existing antifungal resistance mechanisms.
- Further development of G4-targeting agents could provide new therapeutic options against life-threatening fungal infections.
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