Peeling and Sliding in Nucleosome Repositioning

TL;DR

This paper models the combined passive and active mechanisms of nucleosome repositioning, revealing how DNA peeling and motor activity influence histone sliding and detachment dynamics.

Contribution

It introduces a stochastic model coupling passive histone sliding with active motor-driven unwrapping, providing insights into the effects of DNA affinity and motor speed.

Findings

Larger DNA peeling enhances diffusional sliding.

Fast motors tend to cause histone detachment.

Higher DNA affinity increases motor travel distance.

Abstract

We investigate the mechanisms of histone sliding and detachment with a stochastic model that couples thermally-induced, passive histone sliding with active motor-driven histone unwrapping. Analysis of a passive loop or twist defect-mediated histone sliding mechanism shows that diffusional sliding is enhanced as larger portions of the DNA is peeled off the histone. The mean times to histone detachment and the mean distance traveled by the motor complex prior to histone detachment are computed as functions of the intrinsic speed of the motor. Fast motors preferentially induce detachment over sliding. However, for a fixed motor speed, increasing the histone-DNA affinity (and thereby decreasing the passive sliding rate) increases the mean distance traveled by the motor.