Fractionation of chromatin depleted of histone H1.

Chromatin depleted of histone H1 was prepared after extraction with 0.6 M NaCl. The salt-extracted chromatin was mechanically fragmented, then fractionated on sucrose gradients in two fractions, the fast migrating (heavy) and the slow migrating (light) fractions. The average sizes of the DNA-moieties from heavy and light fractions were found to be similar. However, heavy fractions were enriched in high temperature melting populations, whereas, light fractions exclusively included low temperature melting populations, not seen in the heavy fractions. Comparison of the derivative plots of thermally denatured whole and salt-extracted chromatin as well as heavy and light fractions of salt-extracted chromatin suggests that the DNA regions associated with histone H1 in intact chromatin may be co-isolated with the light fraction.