Linker Histone H1 interacts with DNA between nucleosome units in mediating chromatin compaction into higher order structures. Histones are basic nuclear proteins responsible for the nucleosome structure of eukaryotic chromatin. Repeating nucleosome units contain two molecules each of core Histones H2A, H2B, H3, and H4 that form an octamer complex around which approximately 146 base pairs of DNA is wrapped. (NCI) [ ]