FIG. 8.

Activity of FEN on modified pseudo-Y substrates at 50°C. (A) Lanes: 1, marker (FS, 37 nt); 2 and 3, FS after incubation of FS plus FA with Taq DNA polymerase and FEN, respectively; 4 and 5, FS after incubation of FS plus FA-T with Taq DNA polymerase and FEN, respectively (see Fig. 2C); 6 and 7, FS after incubation of FS, FA, and FA-C (hybridized to FA) with Taq DNA polymerase and FEN, respectively (see Fig. 2D). (B) Lanes: 1, 21-nt marker; 2, oligonucleotide FS (37 nt); 3 and 5, FS after incubation of FS plus FA (unmodified substrate) with Taq DNA polymerase and FEN, respectively; 4 and 6, FS after incubation of FS, FA, and FS-C (hybridized to FS) with Taq DNA polymerase and FEN, respectively (see Fig. 2E). (C) Lanes: 1, marker formed by ligating oligonucleotide FS-L to ³²P-labeled FS to form a hairpin loop (see Fig. 2F); 2 to 4, hairpin loop after incubation with Taq DNA polymerase for 5, 15, and 45 min, respectively; 5 to 7, hairpin loop after incubation with FEN for 5, 15, and 45 min, respectively.