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Related Experiment Videos

Sequences in sigmaN determining holoenzyme formation and properties.

M T Gallegos1, M Buck

  • 1Department of Biology, Imperial College of Science Technology and Medicine, Sir Alexander Fleming Building, Imperial College Road, London, SW7 2AZ, UK.

Journal of Molecular Biology
|May 18, 1999
PubMed
Summary

Sigma-N protein in bacterial RNA polymerase holoenzymes binds rare promoters. Its interaction with core RNA polymerase involves extensive regions, influencing enhancer-dependent transcription and heparin sensitivity.

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Area of Science:

  • Bacterial transcription initiation
  • Protein-DNA interactions
  • Enzyme kinetics

Background:

  • Sigma subunits are crucial for bacterial RNA polymerase promoter recognition.
  • Sigma-N (sigmaN) directs holoenzyme to rare promoters, forming transcriptionally inactive complexes.
  • SigmaN-holoenzyme mediates enhancer-dependent transcription.

Purpose of the Study:

  • To investigate the stability and core RNA polymerase binding of sigmaN-holoenzyme.
  • To identify specific regions of sigmaN responsible for core binding and functional properties.
  • To elucidate the mechanism underlying sigmaN-holoenzyme's heparin sensitivity.

Main Methods:

  • Competition and dissociation assays to assess holoenzyme stability.
  • Purification and binding assays of sigmaN fragments with core RNA polymerase.

Related Experiment Videos

  • Heparin dissociation assays to study holoenzyme disruption.

    • Main Results:

    • SigmaN-holoenzyme exhibits stability comparable to sigma70-holoenzyme.
    • Two distinct sigmaN fragments bind the core RNA polymerase with differing affinities.
    • The N-terminal region (Region I) and a Region III fragment contribute to core binding.
    • Heparin disrupts sigmaN-core interaction, explaining heparin sensitivity.

    Conclusions:

    • The sigmaN interface with core RNA polymerase is extensive, involving multiple regions.
    • Core binding via Region I is critical for enhancer responsiveness in sigmaN-holoenzyme.
    • Heparin sensitivity arises from the disruption of the sigmaN-core complex.