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DNA supercoiling-induced shapes alter minicircle hydrodynamic properties.

Radost Waszkiewicz1, Maduni Ranasinghe2, Jonathan M Fogg3

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DNA supercoiling and looping influence its 3-D shape and hydrodynamic properties. This study reveals how negative supercoiling affects DNA

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Area of Science:

  • Molecular Biology
  • Biophysics
  • Biochemistry

Background:

  • DNA in cells is organized into negatively supercoiled loops.
  • Supercoiling and looping induce torsional and bending strain, enabling diverse DNA 3-D structures.
  • DNA structure impacts essential processes like replication, transcription, and repair.

Purpose of the Study:

  • To investigate the impact of negative supercoiling and curvature on DNA hydrodynamic properties.
  • To correlate DNA shape with its behavior in solution.

Main Methods:

  • Analytical Ultracentrifugation (AUC) was used to analyze DNA minicircles (336 bp and 672 bp).
  • Linear elasticity theory was applied to predict DNA shapes.
  • Hydrodynamic calculations were performed to interpret AUC data.

Main Results:

  • Hydrodynamic properties, including diffusion and sedimentation coefficients and hydrodynamic radius, were significantly influenced by circularity, loop length, and supercoiling degree.
  • AUC data showed dependence on DNA topology.
  • Predicted shapes from elasticity theory showed reasonable agreement with experimental AUC data.

Conclusions:

  • Negative supercoiling and DNA looping are critical determinants of DNA shape and solution behavior.
  • A combined theoretical and experimental framework aids in predicting supercoiling's effects on DNA.
  • Understanding these relationships is key to comprehending DNA organization and function.