Figure 4.

The C-tail deletion in TFB2M affects initiation complex formation. A, the promoter fragment LSP used in this study. The two start sites are underlined. B, runoff transcription profiles of TFB2M-WT and the C-tail deletion mutants TFB2M-Δ3 and TFB2M-Δ7 on the LSP promoter (the full gel profile is shown in Fig. S6). Reactions were carried out with 0.6 μm POLRMT, TFAM, and promoter duplex and increasing concentrations of TFB2M-WT or C-tail mutant and 250 μm ATP, UTP, GTP, and γ[³²P]ATP for 15 min at 25 °C in transcription buffer. C, plot showing quantitation of grouped runoff products for each reaction. The error bars represent errors calculated from two independent experiments.