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Updated: Jun 27, 2026
Fluorescence-Based Detection of FEN1 Nuclease Activity and Screening of Small-Molecule Inhibitors
Published on: June 27, 2025
A novel cell-free screen identifies a potent inhibitor of the Fanconi anemia pathway
Igor Landais1, Alexandra Sobeck, Stacie Stone
1Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97239, USA.
Abstract:
The Fanconi Anemia (FA) DNA damage response pathway is involved in the processing of DNA interstrand crosslinks (ICLs). As such, inhibition of the FA pathway could chemosensitize FA-competent tumor cells to commonly used ICL agents like cisplatin. Moreover, suppression of the FA pathway is synthetic lethal with deficiencies in several other DNA repair pathways, suggesting that FA pathway inhibitors could be used in targeted therapies against specific tumors. To identify such inhibitors, we designed a novel in vitro screening assay utilizing Xenopus egg extracts. Using the DNA-stimulated monoubiquitylation of Xenopus FANCD2 (xFANCD2-L) as readout, a chemical library screen identified DDN (2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone) as a novel and potent FA pathway inhibitor. DDN inhibited xFANCD2-L formation in a dose-dependent manner in both extracts and human cells without disruption of the upstream FA core complex. DDN also inhibited the characteristic subnuclear FANCD2 foci formation following DNA damage. Moreover, DDN displayed a greater synergistic effect with cisplatin in a FA-proficient cancer cell line compared to its FA-deficient isogenic counterpart, suggesting that DDN might be a good lead candidate as cisplatin chemosensitizer in both FA-deficient and FA-competent tumors. This system constitutes the first cell-free screening assay for identifying compounds that inhibit the FA pathway and provides a new biochemical platform for mapping the functions of its various components with specific chemical inhibitors.
Insights
Researchers identified DDN, a novel compound, that inhibits the Fanconi Anemia (FA) DNA repair pathway. This discovery offers potential for new cancer therapies by enhancing chemotherapy effectiveness.
Area of Science:
- Molecular Biology
- Cancer Research
- Biochemistry
Background:
- The Fanconi Anemia (FA) pathway is crucial for repairing DNA interstrand crosslinks (ICLs).
- Inhibiting the FA pathway could sensitize cancer cells to ICL agents like cisplatin.
- FA pathway suppression exhibits synthetic lethality with other DNA repair deficiencies, suggesting targeted therapy potential.
Purpose of the Study:
- To identify novel inhibitors of the Fanconi Anemia (FA) DNA damage response pathway.
- To develop a cell-free screening assay for FA pathway inhibitors.
Main Methods:
- Utilized a novel in vitro screening assay with Xenopus egg extracts.
- Monitored DNA-stimulated monoubiquitylation of Xenopus FANCD2 (xFANCD2-L) as a readout.
- Screened a chemical library to identify FA pathway inhibitors.
Main Results:
- Identified DDN (2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone) as a potent FA pathway inhibitor.
- DDN inhibited xFANCD2-L formation and FANCD2 foci in a dose-dependent manner in extracts and human cells.
- DDN showed synergistic effects with cisplatin in FA-proficient cancer cells, indicating potential as a chemosensitizer.
Conclusions:
- DDN is a novel, potent inhibitor of the Fanconi Anemia pathway.
- The cell-free assay is the first of its kind for identifying FA pathway inhibitors.
- DDN shows promise as a chemosensitizer for cisplatin therapy in various tumors.
