Isolation and characterization of the nuclear matrix from the male Xenopus laevis following estrogen administration: kinetics of [3H] uridine incorporation.

At various times following estrogen administration, the nuclear matrix was isolated from the liver of male Xenopus laevis by sucrose gradient centrifugation of nuclei treated with a high-salt buffer and DNase I in the presence of a proteolytic inhibitor (PMSC--phenylmethyl sulfonyl chloride). Electron micrographs of the nuclear matrix demonstrate a sponge-like network attached to a well-defined inner envelope with a ribosome-free outer envelope. Chemical analyses show that the HSB-DNase-treated nuclei consist of 16% DNA, 2% RNA, and 82% protein, a composition that is consistent with that of nuclear matrices isolated from other species. The specific activity of the matrix-associated RNA following estrogen treatment appears to be maximally enhanced after 5 h and decreases until approximately 12 h, when the activity begins to increase again.