AN ASYMMETRIC MODEL FOR THE NUCLEOSOME - A BINDING-SITE FOR LINKER HISTONES INSIDE THE DNA GYRES

Histone-DNA contacts within a nucleosome influence the function of tra ns-acting factors and the molecular machines required to activate the transcription process, The internal architecture of a positioned nucle osome has now been probed with the use of photoactivatable cross-linki ng reagents to determine the placement of histones along the DNA molec ule. A model for the nucleosome is proposed in which the winged-helix domain of the linker histone is asymmetrically located inside the gyre s of DNA that also wrap around the core histones. This domain extends the path of the protein superhelix to one side of the core particle.