When nuclei were treated with the chemotherapeutic agent, cis-Pt(II), they were crosslinked to the extent that their nuclear morphology as assayed by light microscopy was retained even in the presence of SDS. Protein analysis showed that the histones were completely absent from these nuclear structures, while the non-histone proteins, with one possible exception, were completely retained. When the nuclear structures in SDS were treated with thiourea to reverse the crosslinks, the non-histone proteins were liberated and the nuclear structures disappeared. When treated with Proteinase K in SDS, the nuclear structures also disappeared, indicating that protein components were necessary to maintain the structures.
