ABSTRACT
Nuclear matrix is defined as the residuum that remains after the DNA and RNA are digested, the lipids are dissolved with a nonionic detergent, and the histones and many nonhistone proteins are solubilized by high salt. The morphology of the nuclear residues varies whether or not disulfide bonds are produced. When nuclear isolation is done without a sulfhydryl-blocking reagent, the residual structure contains a well-preserved nucleoli and an intranuclear network. The lamina and the pore-complexes are the only well-characterized components of the nuclear residuum. The 68-kilodalton protein was localized by incubating isolated nuclear envelope with antibodies raised against undenatured proteins of Xenopus oocyte nuclear skeleton. Lamina, pore complexes, and nuclear envelope are obtained irrespective of the method used to digest DNA, either by DNAase I or phenanthroline. They are therefore true nuclear entities. Nuclear residues obtained from nuclei isolated in the presence of N-ethylmaleimide contain distorted nucleolar residues and a sparse intranuclear network.
