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Updated: Jun 12, 2025
11:27
Studying DNA Looping by Single-Molecule FRET
Published on: June 28, 2014
15.4K
Symmetry of loop extrusion by dimeric SMC complexes is DNA-tension-dependent
Biswajit Pradhan1, Adrian Pinto2, Takaharu Kanno3,4
1Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany.
Biorxiv : the Preprint Server for Biology
|September 24, 2024
Summary
Structural maintenance of chromosome (SMC) complexes exhibit dynamic DNA loop extrusion symmetry. Dimeric SMCs switch extrusion direction based on DNA tension and thermal fluctuations, challenging fixed symmetry views.
Area of Science:
- Molecular biology
- Genomics
- Biophysics
Background:
- Structural maintenance of chromosome (SMC) complexes are crucial for genome organization.
- DNA loop extrusion by SMCs increases genome loop size, but extrusion symmetry factors are unknown.
Purpose of the Study:
- Investigate the symmetry of DNA loop extrusion by various SMC complexes.
- Determine factors influencing the directionality and symmetry of DNA reeling.
Main Methods:
- Single-molecule analysis
- Molecular dynamic simulations
Main Results:
- Monomeric SMCs (condensin, cohesin) show one-sided extrusion.
- Dimeric SMCs (Smc5/6, Wadjet) exhibit tension-dependent extrusion symmetry.
- At low tension, dimeric SMCs extrude from both sides; at high tension, they switch direction.
- Thermal fluctuations impact reeling rates and direction switching.
Conclusions:
- SMC loop extrusion symmetry is not fixed but dynamic.
- Extrusion symmetry is regulated by intrinsic protein properties and extrinsic factors like DNA tension.
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