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Related Experiment Videos

DNA melting within a binary sigma(54)-promoter DNA complex.

W Cannon1, M T Gallegos, M Buck

  • 1Department of Biology, Imperial College of Science, Technology and Medicine, London SW7 2AZ, United Kingdom.

The Journal of Biological Chemistry
|October 19, 2000
PubMed
Summary

Bacterial RNA polymerase sigma(54) melts promoter DNA upon activator binding, initiating transcription. Activators relieve sigma(54) self-inhibition, enabling DNA melting and transcription complex progression.

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Area of Science:

  • Bacteriology
  • Molecular Biology
  • Biochemistry

Background:

  • Bacterial transcription initiation relies on sigma(54) and enhancer-binding activators.
  • Sigma(54) requires activators for DNA binding and transcription initiation.

Purpose of the Study:

  • To investigate the mechanism by which sigma(54) melts promoter DNA.
  • To elucidate the role of activators in sigma(54)-mediated DNA melting and transcription.

Main Methods:

  • Studied DNA melting by sigma(54) bound to a DNA structure mimicking closed complexes.
  • Investigated the influence of Region I sequences on sigma(54) DNA melting activity.
  • Examined holoenzyme progression from closed to open complexes.

Main Results:

Related Experiment Videos

  • Sigma(54) melts promoter DNA upon activator binding in a nucleotide-hydrolyzing reaction.
  • DNA melting initiates at a nucleation point and spreads towards the transcription start site.
  • Activators promote a conformational change in sigma(54), overcoming self-inhibition and revealing DNA-melting activity.
  • Ordered events involving core-sigma(54) and sigma(54)-DNA interactions facilitate holoenzyme isomerization.

Conclusions:

  • Activator binding is crucial for sigma(54) to melt DNA and initiate transcription.
  • Sigma(54) exists in a self-inhibited state, with activators releasing this inhibition.
  • The study reveals a step-wise mechanism for transcription initiation involving conformational changes and DNA interactions.