Fig. 4. Kinetics of SII-activated transcript cleavage by RNA polymerase II.

Washed elongation complexes were incubated with 2 μg of partially purified bovine brain SII and 7 mM MgCl₂. Incubation proceeded at 28 °C for 0, 2, 5, or 60 min (panel A) or 0, 20, 50, 80, 110, and 300 s (panel B). One sample (panel A, lane 1) was made 0.25% (w/v) in sarkosyl before incubation at 28 °C for 30 min. RNA was isolated and analyzed by electrophoresis as described under “Materials and Methods.” Migration positions of RNAs are indicated as described for Fig. 1.