The DNA (red) is wound around two sets of core histone proteins (green) to form a kind of bead on a string. The H1 histone protein clamps the DNA into place where it enters and exits a bead.

The chain of nucleosomes is then wrapped into a 30 nm spiral called a solenoid, where additional H1 histone proteins are associated with each nucleosome to maintain the chromosome structure.

This regulation takes place in the context of the histone proteins. Two each of the four standard histones - H3, H4, H2A, and H2B - join together to form an octameric nucleosome, a spool around which ...