Isolation and Characterization of the Nuclear Matrix from Zajdela Ascites Hepatoma Cells

A procedure is reported for the isolation of Zajdela ascites hepatoma nuclei which avoids the use of harsh detergents and citric acid. Marker enzyme analysis, chemical composition, and electron microscopy all indicated a high degree of purity and intactness. The proteinaceous nucleoskeletal structure termed the “nuclear matrix” was isolated from the hepatoma nuclei. Structurally, the isolated hepatoma matrix consisted of a surrounding residual nuclear envelope, residual nucleoli, and an extensive internal matrix structure. The internal matrix structure, moreover, revealed a remarkable resemblance to structures observed in the interchromatinic regions of intact hepatoma nuclei. Chemically, the matrix contained 77.9% protein, 19.6% RNA, 1.0% DNA, and 1.5% phospholipid. Nearly identical ultrastructure and composition is found for the corresponding matrices isolated from normal and regenerating liver cells. Although many differences were initially found in the polypeptide profiles of hepatoma and liver matrices, isolation in the presence of the protease inhibitors phenylmethylsulfonyl fluoride and sodium tetrathionate revealed that these apparent differences were largely due to differential degradation of matrix polypeptides. In the presence of protease inhibitors, only one qualitative difference was detected, a polypeptide with a molecular weight of 100,000 unique to the hepatoma matrix. In addition, several prominent quantitative differences were detected. Comparison of regenerating and normal liver matrix polypeptide profiles revealed no significant qualitative or quantitative differences.