FIG. 1.

 Effect of FCP1 on transcription elongation by RNAP II in a reconstituted system. (A) Template DNA sequence and experimental scheme for the isolation of stalled +42 complexes (see Materials and Methods for details). (B) Ternary +42 complexes (washed with Txn100 and equilibrated with Txn60) were incubated alone (lanes 1 to 4) or in the presence of FCP1 (60 ng; lanes 5 to 8) for 10 min at 30°C and then chased with 30 μM concentrations of each of the four XTPs (ATP, GTP, CTP, and UTP). Reactions were stopped at various time points (0, 20, 60, and 180 s, respectively), and then reaction products were subjected to phenol-chloroform extraction and ethanol precipitation, after which were analyzed by electrophoresis on polyacrylamide-urea gels followed by autoradiography.