Figure 6.

Comparison of TFIIF binding to purified Pol II and to Pol II in PICs. TFIIF-FeBABE derivatives were mixed with purified Pol II containing a C-terminal Flag-tagged Rpb2 subunit, and hydroxyl radical production was activated and cleavage visualized by western blot. This was done in parallel with the same TFIIF derivatives incorporated in PICs. (A) FeBABE linked to the TFIIF dimerization domain. (B) FeBABE linked to the Tfg2 winged helix domain. (C) The Pol II–TFIIF dimerization domain model from Figure 3 with cleavage observed in reactions containing purified Pol II and the Tfg2 winged helix-FeBABE derivatives. The cleaved region, highlighted in blue, shows that the winged helix binds near the Pol II lobe in the Pol II–TFIIF complex. Cleavage data are from Supplementary Table S3.