Conversion of the omega subunit of Escherichia coli RNA polymerase into a transcriptional activator or an activation target

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Abstract
Evidence obtained in both eukaryotes and prokaryotes indicates that arbitrary contacts between DNA-bound proteins and components of the transcriptional machinery can activate transcription. Here we demonstrate that the Escherichia coli ω protein, which copurifies with RNA polymerase, can function as a transcriptional activator when linked covalently to a DNA-binding protein. We show further that ω can function as an activation target when this covalent linkage is replaced by a pair of interacting polypeptides fused to the DNA-binding protein and to ω, respectively. Our findings imply that the ω protein is associated with RNA polymerase holoenzyme in vivo, and provide support for the hypothesis that contact between a DNA-bound protein and any component of E. coli RNA polymerase can activate transcription.