Phen-DC3 Trifluoromethanesulfonate is a G-quadruplex (G4) specific ligand that inhibits FANCJ and DinG helicases with IC50s of 65±6 nM and 50±10 nM, respectively.

DinG helicases (G4 substrate):50±10 nM, FANCJ helicase (G4 substrate):65±6 nM

The CEB25-L111(T) array remains stable in wild-type (WT) cells but exhibits instability when treated with Phen-DC3 Trifluoromethanesulfonate or upon PIF1 gene deletion. Similarly, the CEB1-WT array, while generally stable, shows frequent rearrangements after exposure to 10 μM Phen-DC3 Trifluoromethanesulfonate in WT cells. The c-Myc allele is significantly destabilized following Phen-DC3 Trifluoromethanesulfonate treatment or PIF1 deletion, revealing high susceptibility to destabilization under these conditions. Meanwhile, the CEB1-loop CEB25 allele maintains full stability in both scenarios involving PIF1 treatment or in WT cells, indicating a distinct response to these genetic interventions.