Fig. 6. NF1 protein enhances proper termination of transcription by RNA polymerase III in conjunction with TFIIIC. (A) Each reaction contained 20 fmol of C-tailed VA1 template and 25 fmol of immunopurified RNA polymerase III. The reaction mixtures were supplemented with no additional factors (lane 1), 200 fmol of holo TFIIIC (lanes 2 and 7), 200 fmol of core TFIIIC (lanes 3–5 and 8–11), 100 ng of recombinant PC4 (lanes 9–11), or 1 (lanes 4, 10 and 12) or 3 (lanes 5, 11 and 13) µl of the purified NF1. Transcripts terminated at the first terminator site (T1), the second terminator site (T2) or the end of the template (RT) are indicated on the right. (B) Diagram of the C-tailed VA1 template and derived transcripts. The positions of the two T stretches, T1 and T2, are indicated with arrows.