Figure 4.

Time-course of transcription elongation by T7 RNA polymerase. (A) Autoradiogram of a 5% polyacrylamide/7 M urea gel showing the run-off (RO) and terminated (T) transcripts obtained with T7 RNA polymerase. The reaction contained 1 µg of template pDBP-term2(F) linearised with HindIII, 160 ng of recombinant mtDBP and 5 U of T7 RNA polymerase. After a pulse-label of 5 min with [α^-32P]UTP, the reaction was chased with an excess amount of unlabelled UTP and samples were taken at the time points indicated. The ratio of labeling of the terminated to the run-off transcript is indicated for each time point. (B) Image of the same gel as in (A) stained with ethidium bromide.