FIG. 4.

Srs2 unwinds a TNR substrate substantially faster than does UvrD. DNA substrates radiolabeled on the shorter strand were incubated with either Srs2 (35 nM) or UvrD (200 nM) under standard conditions (19, 30) for the indicated times, and the reaction products were separated by PAGE and visualized by phosphorimaging. Both DNA substrates contained a 14-nucleotide-long 3′ tail, which is usable by either Srs2 or UvrD. (A) Schematic diagram of the (CTG)₁₀-containing substrate. Along with the 9 bp of nonrepeating DNA (identical to Fig. 3C), the duplex region is 39 bp in total length. (B) Control substrate (19) without triplet repeats. The duplex region measures 40 bp.