Transcription-driven twin supercoiling of a DNA loop: a Brownian dynamics study

Area of Science:

• Molecular Biology
• Biophysics
• Computational Biology

Background:

• RNA polymerase movement along DNA generates torque, potentially causing significant DNA structural deformations.
• These deformations are crucial for various biological processes in both prokaryotes and eukaryotes.
• Understanding DNA mechanics under torsional stress is vital for comprehending gene regulation and DNA processing.

Purpose of the Study:

• To introduce and utilize a dynamic computer model for investigating torque-induced DNA structural deformations.
• To simulate the response of DNA to localized torsional stress generated by the transcription machinery.
• To analyze the resulting supercoiling and its implications for DNA structure and function.

Main Methods:

• Developed a dynamic computer model representing double-stranded DNA as a chain of hydrodynamic beads.
• Employed potentials for stretching, bending, twisting, and excluded volume interactions.
• Simulated DNA response to applied torque using Brownian dynamics for a 477-base pair B-DNA template.

Main Results:

• Simulations revealed that torsional stress leads to supercoiling deformations, with stress partitioning between twist and writhe.
• Observed simultaneous right-handed and left-handed superhelicity in adjacent DNA subdomains, consistent with the twin-supercoiled-domain model.
• Generated torsional stress was sufficient to drive secondary structural transitions in DNA.

Conclusions:

• The dynamic model accurately captures transcription-induced DNA supercoiling and structural changes.
• DNA exhibits complex superhelical deformations under torsional load, with implications for DNA mechanics.
• The findings support the transcription-induced twin-supercoiled-domain model and highlight the role of DNA mechanics in biological regulation.