BASE-SPECIFIC RECOGNITION OF THE NONTEMPLATE STRAND OF PROMOTER DNA BY ESCHERICHIA-COLI RNA-POLYMERASE

RNA polymerase recognizes its promoters through base-specific interact ion between defined segments of DNA and the sigma subunit of the enzym e. This interaction leads to separation of base pairs and exposure of the template strand for RNA synthesis. We show that base-specific reco gnition by the sigma(70) holoenzyme in this process involves primarily nontemplate strand bases in the -10 promoter region. We suggest that melting involves the persistence of these contacts as the bound duplex (closed) form is converted to the single-stranded (open) form of the enzyme-promoter complex.