[Localization of histone H1 in chromatin. Cross-linking of the N- and C-terminal halves of the molecule with bifunctional reagents].

Mutual arrangement of histone H1 molecules was studied in calf thymus nuclei, extended chromatin and chromatin, isolated and kept in 8 M urea. Histone H1 dimers crosslinked with methyl 4-mercaptobutyrimidate were digested with chymotrypsin and crosslinked fragments obtained were analysed by diagonal gel electrophoresis. In all chromatins tested the N- and C-terminal parts of the H1 molecules were crosslinked in all possible combinations, i.e. C-C, C-N and N-N. These and related data obtained earlier indicate, that the proximity of histone H1 molecules in chromatin is determined by the structure of nucleosomal chain itself and not by chromatin superstructure. The results also suggest that the H1A and H1B subfractions of histone H1 are interspersed in extended nucleosomal chains.