Bend-Induced Twist Waves and the Structure of Nucleosomal DNA

TL;DR

This paper demonstrates that twist-bend coupling causes intrinsic sinusoidal twist waves in bent DNA, explaining nucleosomal DNA structure and suggesting these features are inherent to DNA mechanics rather than solely protein interactions.

Contribution

It provides an analytical solution showing twist-bend coupling induces twist waves in bent DNA, supported by simulations and nucleosomal data, revealing an intrinsic DNA property.

Findings

Twist-bend coupling causes sinusoidal twist waves in bent DNA.

Observed twist oscillations in nucleosomal DNA are intrinsic, not solely due to histone interaction.

Analytical results agree with simulations and experimental data.

Abstract

Recent work indicates that twist-bend coupling plays an important role in DNA micromechanics. Here we investigate its effect on bent DNA. We provide an analytical solution of the minimum-energy shape of circular DNA, showing that twist-bend coupling induces sinusoidal twist waves. This solution is in excellent agreement with both coarse-grained simulations of minicircles and nucleosomal DNA data, which is bent and wrapped around histone proteins in a superhelical conformation. Our analysis shows that the observed twist oscillation in nucleosomal DNA, so far attributed to the interaction with the histone proteins, is an intrinsic feature of free bent DNA, and should be observable in other protein-DNA complexes.