Termination, Release, and Reinitiation of RNA Chains from DNA Templates by Escherichia coli RNA Polymerase

Abstract

Transcription of DNA in vitro by Escherichia coli RNA polymerase can be divided into several discrete steps. These include (a) recognition by the polymerase of specific starting sites on the template DNA at which enzyme molecules bind and (b) initiation of RNA chains. It has been shown previously (Maitra and Hurwitz, 1965) that the initiation reaction, measured by the incorporation of γ-32P-labeled nucleoside triphosphates, leads to the formation of RNA chains in which the first nucleotide retains the 5′-triphosphate end. Purine nucleoside triphosphates, ATP and GTP, are the only triphosphates beginning an RNA chain. Recently Burgess et al. (1969) have described an initiation subunit σ (sigma) factor, which can be dissociated from the polymerase complex by phosphocellulose chromatography. This protein factor has been shown to be involved in RNA chain initiation with native T4 and T7 DNA templates. The next steps involve (c) elongation of RNA chains by the addition...