Interaction betweenE. coliRNA polymerase and thetetRpromoter from pSClOl: homologies and differences with otherE. colipromoter systems from close contact point studies

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Abstract
The interaction between E.coli RNA polymerase and the tetR promoter from pSCIOI, was studied by protection and premodification experiments, using dimethyl sulfate, methylation of single stranded cytosines, and DNAase I footprinting. Whereas qualitative and quantitative results from the chemical approach conform to patterns already displayed by other promoter systems, hypersensitive sites to DNAase I attack differ from those of other promoters. Distribution and nature of the contacts suggest that regions of the promoter sequence participates differently in complex formation. The involvement of major and minor grooves of the double helix in the complex with the enzyme, differs along the promoter. After a comparison of the results from seven different promoters, a pattern of conserved contacts seem to appear. Comparison of temperature dependence of local unwinding around the transcription start site (detected by the appearence of 3ingle stranded cytosines), and DNAasel footprinting, reveals that the process leading to stable complex formation can be achieved without disruption of base-pairing.