FANCJ-A349P mutant is inactive as a helicase on forked duplex and G-quadruplex DNA substrates that FANCJ-WT efficiently unwinds. (A) Helicase reactions (20 μL) were performed by incubating the indicated FANCJ concentration with a 0.5nM forked duplex DNA substrate at 30°C for 15 minutes as described in supplemental Methods. Triangle, heat-denatured DNA substrate control. (B) Helicase reactions were performed the same as with panel A, except that G4 DNA was used instead of forked duplex. M, radiolabeled TP-G4 49-mer oligonucleotide (supplemental Table 1) marker.