Reversible Oligonucleosome Self-Association:  Dependence on Divalent Cations and Core Histone Tail Domains

Regularly spaced nucleosomal arrays equilibrate between unfolded and highly folded conformations in > 10 000 S. Importantly, all steps in the self-association pathway are freely reversible upon removal of the divalent cations. Taken together, these data indicate that short oligonucleosome fragments composed of only core histone octamers and DNA possess all of the structural features required to achieve chromosome-level DNA compaction. These findings provide a molecular basis for explaining many of the recently uncovered structural features of interphase and metaphase chromosomal fibers.