Histone H1 affects the loss of chromatin fragments from nuclease-treated nuclei.

During nuclease treatment of nuclei in 80 mM buffers, a frequently used technique for solubilizing chromatin, oligonucleosomes escape the nucleus and are commonly discarded. These released oligonucleosomes lack H1 histone. Their loss of histone is easily explained by the recently described exchange of H1 that takes place at such ionic strengths. A comparison of H1-depleted nuclei to complete nuclei indicates that the presence of H1 on the oligonucleosomes prevents their escape from the nucleus. Even core particles (140-150 base pairs of DNA) are preferentially retained in the nucleus of H1.