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Interplay between DNA sequence and negative superhelicity drives R-loop structures.

Robert Stolz1,2, Shaheen Sulthana1, Stella R Hartono1

  • 1Department of Molecular and Cellular Biology, University of California, Davis, CA 95616.

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Summary
This summary is machine-generated.

R-loops form during transcription and are influenced by DNA sequence and topology. This study models R-loop formation, revealing how DNA superhelicity and base pairing control their stability and function as topology sinks.

Keywords:
DNA topologyR-loopmodelingtranscription

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Area of Science:

  • Molecular Biology
  • Biophysics
  • Genetics

Background:

  • R-loops are three-stranded nucleic acid structures formed during transcription.
  • DNA sequence and topology are known to affect R-loop formation, but their interaction is not fully understood.

Purpose of the Study:

  • To investigate the interplay between DNA sequence and topology in controlling R-loop formation and stability.
  • To develop a model predicting R-loop susceptibility based on these factors.

Main Methods:

  • Developed a statistical mechanical equilibrium model for R-loop formation in superhelical DNA.
  • Utilized in vitro transcription assays to observe R-loop formation and plasmid relaxation.
  • Employed single-molecule R-loop footprinting to map stable R-loop positions.

Main Results:

  • The model identified junctional, base-pairing, and superhelicity energies as key factors in R-loop formation.
  • R-loops were shown to absorb negative superhelicity, relaxing the DNA domain.
  • Experimental data confirmed theoretical predictions on R-loop stability and topological impact.

Conclusions:

  • DNA sequence and superhelicity critically control R-loop stability.
  • R-loops act as reversible topology sinks, potentially relieving transcriptional superhelical stress nonenzymatically.