Hepatoma-associated non-histone proteins are phosphoproteins preferentially localized in nuclear matrix

Diversity of nuclear protein fractions of hamster liver and hepatoma produced by DNaseI

The structural and functional diversity between active and inactive chromatin is thought to depend, in part, upon differences in DNA-bound protein composition, including changes in the number of sulfhydryl groups. The aim of the present study was to compare protein composition in untreated nuclei, DNaseI-released and resistant nuclear fractions of hamster liver and Kirkman-Robbins hepatoma cells. Electrophoretic analysis of nuclear proteins showed some evident quantitative and qualitative differences between normal and neoplastic cells. The most significant diversities were noticed in DNaseI solubilized fraction of both types of cells. Nuclease attack released a characteristic set of non-histones with mol. wt 37,000, 50,000, 74,000 and 130,000-160,000 from transformed cells, and polypeptides of mol. wt 45,000 and 76,000 from normal cells. Cell-specific distribution within examined nuclear polypeptides was revealed using selective staining of their protein-bound sulfhydryls. Immunoblot analysis demonstrated that a non-histone protein with mol. wt 48,000, overexpressed in rodent tumour cells, was exclusively concentrated in liver DNaseI-sensitive fraction, which amounted only to 8.3% +/- 2.0% of total nuclear DNA. In hepatoma cells, however, this particular polypeptide is distributed between nuclease-sensitive and nuclease-resistant nuclear fractions. Non-histone protein of mol. wt 48,000 appeared to contain free sulfhydryl groups. In summary, these results show molecular specificity of nuclear proteins from normal and tumour cells and differences in their distribution among nuclease-released and nuclease-resistant nuclear fractions. The diversity in molecular characteristics and sulfhydryl group patterns observed among the examined proteins of normal and neoplastic cells may suggest their involvement in some changes in the rearrangement of nuclei during neoplastic transformation.

Electrophoretic analysis of nuclear matrix proteins and the potential clinical applications

Nuclear matrix proteins form the skeleton of the nucleus and participate in the various cellular functions of the nucleus. These proteins have been demonstrated to be tissue-type specific and can potentially reflect changes in the state of differentiation of the cell. Elucidating nuclear matrix protein changes necessitates the use of high-resolution two-dimensional polyacrylamide gel electrophoresis. Separation of this complex mixture into its component parts resolves protein changes when comparing the normal state to a diseased state of a cell. Evidence has been reviewed which shows the potential use of nuclear matrix proteins and antibodies to nuclear matrix proteins as diagnostic tools for various cancers, autoimmune diseases, adenoviral infection, and other diseases. Consequently, the central functions of the nuclear matrix in the cell allow it to have significant potential as a diagnostic agent.

Hepatoma-associated nuclear matrix nonhistone antigens

Polyclonal antibodies generated against a group of high molecular weight nonhistone proteins from Morris hepatoma 7777 were used in immunological studies of hepatoma-associated nonhistone proteins in rat and hamster. We revealed the presence of cross-reactive antigens in rat Morris hepatomas 7777 and 8994, and in hamster Kirkman-Robbins hepatoma, but not in normal rat or hamster livers. These specific nonhistone proteins were found to be preferentially localized in the nuclear matrix of rat Morris hepatoma 7777 as well as hamster Kirkman-Robbins hepatoma.