Dynamics of DNA in chromatin and DNA binding mode to core protein.

We have studied the dynamics of DNA in nucleosome core particles and in the linker region of chromatin using nanosecond fluorescence anisotropy decay measurements of intercalated ethidium. DNA in the core undergoes torsional motions to the same extent as the linker DNA in extended chromatin. We therefore concluded that the binding of DNA to the histone octamer is relatively weak or limited to a few points; stretches of at least several tens of base pairs exist which can move as freely as DNA in solution.