  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.
