Fig. 1.

Schematic of EcoRNAPσ⁷⁰. (A) σ_1.1 is present in the active site channel but displaced during open complex formation allowing downstream DNA binding (B). (C) EcoRNAPσ⁷⁰ is complexed with Gp2, which interacts with the β′ jaw and σ_1.1, blocking downstream DNA binding and open complex formation. (Adapted from ref. 8.) (D) Schematic representation of the yeast RNAPII 32-protein preinitiation complex. RNAPII is depicted in gray at the bottom. The general transcription factors are depicted at the top with the C terminus of Ssl2, a component of TFIIH, extending over the cleft to interact with polII and preventing the DNA from entering the cleft. (Adapted from ref. 15.)