Positioning of two alpha subunit carboxy-terminal domains of RNA polymerase at promoters by two transcription factors.

Interactions between the cAMP receptor protein (CRP) and the carboxy-terminal regulatory domain (CTD) of Escherichia coli RNA polymerase alpha subunit were analyzed at promoters carrying tandem DNA sites for CRP binding using a chemical nuclease covalently attached to alpha. Each CRP dimer was found to direct the positioning of one of the two alpha subunit CTDs. Thus, the function of RNA polymerase may be subject to regulation through protein-protein interactions between the two alpha subunits and two different species of transcription factors.