CONVERSION OF THE OMEGA-SUBUNIT OF ESCHERICHIA-COLI RNA-POLYMERASE INTO A TRANSCRIPTIONAL ACTIVATOR OR AN ACTIVATION TARGET

Evidence obtained in both eukaryotes and prokaryotes indicates that ar bitrary contacts between DNA-bound proteins and components of the tran scriptional machinery can activate transcription. Here we demonstrate that the Escherichia coli omega protein, which copurifies with RNA pol ymerase, can function as a transcriptional activator when linked coval ently to a DNA-binding protein. We show further that omega can functio n as an activation target when this covalent linkage is replaced by a pair of interacting polypeptides fused to the DNA-binding protein and to omega, respectively. Our findings imply that the omega protein is a ssociated with RNA polymerase holoenzyme in vivo, and provide support for the hypothesis that contact between a DNA-bound protein and any co mponent of E. coli RNA polymerase can activate transcription.