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Energy required to pinch a DNA plectoneme
Céline Barde1, Nicolas Destainville1, Manoel Manghi1
1Laboratoire de Physique Théorique, IRSAMC, Université de Toulouse, CNRS 118 route de Narbonne, F-31062 Toulouse, France, EU.
Physical Review. E
|May 20, 2018
Summary
DNA supercoiling influences plectoneme formation. Bringing DNA strands closer requires energy, but plectoneme slithering is the likely rate-limiting step for protein binding.
Area of Science:
- Biophysics
- Molecular Biology
- Genetics
Background:
- DNA supercoiling is crucial for biological processes.
- Plectonemes are DNA superhelices formed by supercoiling.
- Simultaneous binding to opposite DNA strands requires proximity.
Purpose of the Study:
- To calculate the energetic barrier for bringing opposed DNA strands in a plectoneme closer.
- To analyze how this energy barrier scales with DNA supercoiling.
Main Methods:
- Analytic calculation of elastic energy barriers.
- Examination of scaling with supercoiling density.
Main Results:
- The energy barrier to pinch a plectoneme is in the kBT range under physiological conditions.
- This energy barrier is dependent on DNA supercoiling levels.
Conclusions:
- The energetic cost of bringing opposed DNA strands together in a plectoneme is biologically accessible.
- Plectoneme slithering, preceding strand proximity, is likely the rate-limiting step for genetic regulatory protein binding.
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