[Localization of histone H1 in chromatin. Cross-linking of central globular regions of H1 molecules with a bifunctional reagent].

Mutual arrangement of histone H1 molecules and central globular parts of H1 was studied by crosslinking with a reversible bifunctional reagent. The yields of histone H1 dimers and dimers of it's globular fragment in nuclei and isolated chromatin were similar. In the presence of 8 M urea the yield of the H1 dimers was approximately threefold decreased, dimers of globular fragment being practically absent. The data suggest that the proximity of H1 molecules in nuclei is stipulated by a structure of a nucleosomal chain itself and not by chromatin superstructure. The results are in accord with the "head" to "head" histone H1 orientation within the nucleosomal chain and do not support participation of the central globular region of H1 molecule in chromatin condensation. A model of H1 arrangement in extended nucleosomal chain is proposed.