Functional interaction between RNA polymerase α subunit C-terminal domain and σ⁷⁰ in UP-element- and activator-dependent transcription

We show that the Escherichia coli RNA polymerase (RNAP) α subunit C-terminal domain (αCTD) functionally interacts with σ⁷⁰ at a subset of UP-element- and activator-dependent promoters, we define the determinants of αCTD and σ⁷⁰ required for the interaction, and we present a structural model for the interaction. The αCTD-σ⁷⁰ interaction spans the upstream promoter and core promoter, thereby linking recognition of UP-elements and activators in the upstream promoter with recognition of the -35 element in the core promoter. We propose that the αCTD-σ⁷⁰ interaction permits UP-elements and activators not only to "recruit" RNAP through direct interaction with αCTD, but also to "remodel" RNAP-core-promoter interaction through indirect, αCTD-bridged interactions with σ⁷⁰.