(a) Engineered transcription templates used here and in ref. 14. Templates carry a sequence of eight repeat motifs (pink) that begins ~1100 bp beyond a T7 A1 promoter (dark green), from which transcription was initiated, and ends ~80 bp before an rrnB T1 terminator (yellow). Templates were labeled with digoxigenin on the transcriptionally upstream end (for assisting loads; solid orange) or the transcriptionally downstream end (for hindering loads; transparent orange). Repeat motifs (red arrow) consist of leader sequence (pink) together with an ops pause sequence (gray), flanked by sequence elements from the rpoB gene (light green) and DNA derived from sites used in cloning (blue).
(b) Average log dwell-time histogram of aligned data (acquired at 1 mM ATP, CTP, and UTP, plus 250 μM GTP, ~23 °C under 7.5 pN assisting load) computed from all repeats of the motif in the absence (red; N = 16 molecules, 81 records) or in the presence of NusG (blue; N = 14 molecules, 81 records), plotted along with bootstrapped standard deviations (white zones). The major pause sites are labeled. The table below shows pause statistics computed for the three most prominent pause sites in the repeat (a, d, and ops) in the presence or absence of NusG.
(c) Average log dwell-time histogram for aligned data (acquired at 1 mM NTPs, ~27 °C, and 5 pN hindering load) computed from all 8 repeats of the ops repeat motif in the absence of NusG (red; N = 36 molecules, 175 records) and in the presence of NusG (blue; N = 13 molecules, 49 records), plotted with the bootstrapped standard deviations (white zones). The table below shows pause statistics computed for the three most prominent pause sites in the repeat (a, d, and ops) in the presence or absence of NusG.