Increased stability of the higher order structure of chicken erythrocyte chromatin: nanosecond anisotropy studies of intercalated ethidium

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Abstract
Internal motion of the DNA in chicken erythrocyte chromatin fibers was studied by measurement of the fluorescence anisotropy decay of ethidium intercalated in the linker region. A comparison of the decay curves of the dye in chicken erythrocyte chromatin with those of calf thymus chromatin [Ashikawa, I., Kinosita, K., Jr., Ikegami, A., Nishimura, Y., Tsuboi, M., Watanabe, K., Iso, K., and Nakano, T. (1983)] revealed greater suppression of nucleosome movement in chicken erythrocyte chromatin. The transition of this chromatin to the compact (solenoidal) structure occurred at lower solvent concentrations of Na+ or Mg2+ than those for calf thymus chromatin. There was increased stability of the higher order structure (the solenoid) of chicken erythrocyte chromatin, which may be related to the reduction of nuclear activity in the chicken erythrocyte cell. The structural transitions of H1-depleted and HI, H5-depleted chromatins were studied. Histone H5 of this chromatin stabilizes the higher order structure in the presence of Mg (or divalent) and did not induce the transition in the solution containing only Na+.