Fig. 4. (A) Transcription of pT72G (lanes 1–6) or pT72G-T (lanes 7–12) in the presence of the NTPs indicated. Normal and poly(G) transcript lengths are indicated. (B) Exo III digestion of ITCs formed with 5′-template strand-labeled pT72G (lanes 2–6) or pT72G-T (lanes 7–11), with the RNA lengths indicated over each lane. The template strand sequence is given next to the Maxam–Gilbert (G+A) sequencing reaction shown in lane 1. Promoter positions at which exo III is halted by the TCs are given to the right of lane 11. (C) Transcription of pT73G (lanes 1–6) or pT73G-T (lanes 7–12) in the presence of the NTPs indicated. Normal and poly(G) transcript lengths are as indicated. (D) Exo III digestion of ITCs formed with 5′-template strand-labeled pT73G (lanes 1–6) or pT73G-T (lanes 7–12), with the RNA lengths indicated above each lane. Promoter positions at which exo III is halted by the TCs are given to the right of lane 12.