Article: article from journal or magazin.
The apical localization of transcribing RNA polymerases on supercoiled DNA prevents their rotation around the template.
Publication types: Journal Article ; Research Support, Non-U.S. Gov't Publication Status: ppublish
The interaction of Escherichia coli RNA polymerase with supercoiled DNA was visualized by cryo-electron microscopy of vitrified samples and by classical electron microscopy methods. We observed that when E. coli RNA polymerase binds to a promoter on supercoiled DNA, this promoter becomes located at an apical loop of the interwound DNA molecule. During transcription RNA polymerase shifts the apical loop along the DNA, always remaining at the top of the moving loop. This relationship between RNA polymerase and the supercoiled template precludes circling of the RNA polymerase around the DNA and prevents the growing RNA transcript from becoming entangled with the template DNA.
Binding Sites, DNA, Bacterial/genetics, DNA, Bacterial/metabolism, DNA, Superhelical/genetics, DNA, Superhelical/metabolism, DNA-Directed RNA Polymerases/metabolism, DNA-Directed RNA Polymerases/ultrastructure, Escherichia coli/enzymology, Escherichia coli/genetics, Freezing, Microscopy, Electron, Models, Structural, Nucleic Acid Conformation, Promoter Regions, Genetic, Protein Conformation, Templates, Genetic, Transcription, Genetic
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