In E. coli, most transcription activators work by making contacts with either the a subunit of RNA polymerase (Class-l transcription activators) or with the cs factor (Class-IU). The Ada protein, a transcriptional activator for a set of genes involved in repair of DNA alkylation damage, has been identified as a Class-l activator, since deletions in the C-terminal domain of the a subunit severely impair Ada activation at the ada promoter. We have shown that the C-terminal domain of a is in fact responsible for binding of RNA polymerase to the promoter region of the ada and the aidB genes.
This observation suggests that the role played by the a subunit of RNA polymerase at these promoters is to interact with the promoter DNA rather than with the transcriptional activator Ada. This possibility would suggest a novel mechanism for RNA polymerase interaction with positively controlled promoters.
In this proposal, we outline a series of experiments to determine if a-mediated binding of RNA polymerase to the ada and aidB promoters is necessary for Ada-activated transcription.