Organization of nucleoskeleton and its relation to DNA topological organization

The organization of nucleoskeleton fibers and its relation to DNA organization in the interphase micronucleus of a ciliate (Stylonychia mytilus Muller) were investigated mainly by the macromolecular spreading procedure combined with electron microscopy. It was shown that the nucleoskeleton fibers are organized as a regular organization termed the nucleoskeleton subunit which is composed of a structural center and a number of branch-like fibers extending radiately from the center. The whole micronuclear skeletal network is composed of a number of the essential subunits which are connected with each other. The micronuclear DNA is closely associated with the nucleoskeleton subunit and constructed as highly ordered DNA loops which appear in some different forms of topological organization. After the DNA-rich nucleoskeleton is digested with proteinase K, the nucleoskeleton subunit disappears, while the DNA loses its regular organization and becomes very random and loose, which suggests that the nucleoskeleton subunit plays very important roles in maintaining the topological organization of the interphase DNA. The nucleoskeleton subunit may be the essential organizational and functional unit of the interphase nucleoskeleton.