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Related Experiment Video

Updated: May 19, 2026

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

Published on: September 27, 2024

MACRO-MOLECULAR CROWDING FAVORS WRITHE IN UNWOUND DNA.

Jin Qian¹, Zachary Z Montgomerie², Andrew J Spakowitz^2,3,4,5

¹Department of Physics, Emory University, Atlanta, GA 30322. Current address: NIDDK, Bethesda, MD 20892, USA.

Biorxiv : the Preprint Server for Biology

|May 18, 2026

Summary

Macromolecular crowding induces a contractile force on DNA, promoting compact, plectonemic forms. This force depends on crowder concentration and molecular weight, influencing DNA conformation within the cell.

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Area of Science:

Biophysics
Molecular Biology
Genomics

Background:

Genomic DNA experiences mechanical and entropic forces, including those from macromolecular crowding in the nucleus.
The cellular environment is densely packed with macromolecules, influencing DNA behavior.

Purpose of the Study:

To investigate the interplay between tension, torsion, and macromolecular crowding on DNA conformation.
To understand how intracellular crowding affects DNA structural transitions.

Main Methods:

Experimental manipulation of DNA with pharmaceutically relevant crowders (Dextran 70, PEG).
Theoretical modeling of DNA equilibrium between B- and L-forms.
Fitting experimental data to a model for DNA conformational transitions.

Main Results:

Macromolecular crowding opposed tension and promoted plectoneme formation in unwound, stretched DNA.
Crowding induced a contractile force on DNA, favoring writhe.
The induced force was dependent on crowder concentration and molecular weight.

Conclusions:

Macromolecular crowding influences DNA conformation, favoring compact, plectonemic forms.
Crowding generates a contractile force impacting DNA structure, relevant to cellular processes.
Understanding these forces is crucial for comprehending DNA organization and function in vivo.