Bend-Induced Twist Waves and the Structure of Nucleosomal DNA

Abstract

Recent work indicates that twist-bend coupling plays an important role in DNA micromechanics. Here we show that this coupling induces standing twist waves in bent DNA, and we provide an analytical solution of the minimum-energy shape of a bent double-helical molecule. This solution is in excellent agreement with both coarse-grained simulations of DNA minicircles and experimental structural data for nucleosomal DNA, 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.