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Author Notes:

To whom correspondence should be addressed. Tel: +1 404 727 8036; Email: ddunlap@emory.edu

Kathleen Matthews generously provided the LacI protein.

Conflict of interest statement. None declared.

Subjects:

Research Funding:

National Institutes of Health [GM084070, 1R15GM109254]. Funding for open access charge: National Institutes of Health [GM084070].

Keywords:

  • Science & Technology
  • Life Sciences & Biomedicine
  • Biochemistry & Molecular Biology
  • TETHERED-PARTICLE MOTION
  • ESCHERICHIA-COLI
  • LAC REPRESSOR
  • BACTERIAL CHROMOSOME
  • HU PROTEIN
  • TRANSCRIPTION
  • MOLECULE
  • FORCE
  • BINDING
  • CHROMATIN

Protein-mediated looping of DNA under tension requires supercoiling

Tools:

Journal Title:

Nucleic Acids Research

Volume:

Volume 46, Number 5

Publisher:

, Pages 2370-2379

Type of Work:

Article | Final Publisher PDF

Abstract:

Protein-mediated DNA looping is ubiquitous in chromatin organization and gene regulation, but to what extent supercoiling or nucleoid associated proteins promote looping is poorly understood. Using the lac repressor (LacI), a paradigmatic loop-mediating protein, we measured LacI-induced looping as a function of either supercoiling or the concentration of the HU protein, an abundant nucleoid protein in Escherichia coli. Negative supercoiling to physiological levels with magnetic tweezers easily drove the looping probability from 0 to 100% in single DNA molecules under slight tension that likely exists in vivo. In contrast, even saturating (micromolar) concentrations of HU could not raise the looping probability above 30% in similarly stretched DNA or 80% in DNA without tension. Negative supercoiling is required to induce significant looping of DNA under any appreciable tension.

Copyright information:

© The Author(s) 2018.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/).

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