The Transcriptional Activator Protein FIS: DNA Interactions and Cooperative Interactions with RNA Polymerase at the Escherichia coli rrnBP1 Promoter

Abstract

The E. coli rrnBP1 promoter oves its stgrength, in part, to the transcriptional activator protein FIS, FIS binds to three sites upsteam of the RNA polymerase (RNAP) binding site and increases transcription in vivofour to ten-fold. In this report, hydroxyl radical and DMS footprinting analyses show that FIS binds to its three sites along one side of the DNA helix, and that FIS bound at the promoter-proximal site (site I) and RNAP bound at the promoter are in close proooooximity. The binding of FIS at site I and RNAP at the promoter are mutually cooperative. These observations support a model for direct interaction between the FIS protein bound at site I and RNAP in transcription activation at rrnBP1. We also find that FIS does not bind cooperatively to its three sites upsteam of rrnBP1, and that the relatively small activation associated with FIS bound at sites II and III does not result indirectly by facilitation of binding of FIS to site I.