Formation of compact globular particles in interphase nuclei from rat liver under the effect of polyanions

Treatment of the isolated nuclei with polyanions (PA) (heparin and dextran-sulfate) at the PA/DNA ratio of about 1 in the 0.15-0.5 M ammonium acetate solution leads to rearrangement of the chromatin structure and formation of compact globular particles (GP) 40-70 nm in diameter, bound by fibrils of variable thickness (2-10 nm). GP formation is accompanied by a loss of nucleosomal periodicity in DNA organization. However, no considerable loss of the DNA contents has been found. At the PA/DNA ratio of more than 2, destruction of the DNP-network and aggregation of GP in larger globular structures are observed. The same effect is observed under the nuclease treatment. Under this condition nuclei lose a considerable part of DNA, but retain histones supposedly as histone-PA aggregates. Therefore the joint effect of PA and salt on nuclei at certain conditions may lead to formation of artefact structures.