Phosphorylation and biosynthesis of high molecular weight proteins of tumor nuclear matrix

Our previous studies showed a predominance of high molecular weight protein group in tumor nuclear matrices. Contrary to normal cells, proteins of this group are preferentially phosphorylated. Phosphoproteins of hepatoma nuclear matrix are selectively subjected to rapid proteolysis. By alkali treatment and a monoclonal antibody against phosphotyrosyl residue the presence of two high molecular weight bands of phosphotyrosyl-containing proteins was detected in nuclear matrices of tumor but not of normal liver cells. High molecular weight protein group of tumor nuclear matrices revealed also a rapid turnover and preferential incorporation of labeled amino acids selectively inhibited by chloramphenicol.

[Effect of colostrum polypeptide on structure and lipid peroxidation in liver nuclei of rats late after gamma-irradiation]

Rats were irradiated by 8Gr in a doze power of 2.33 R per second. A portion of animals were injected subcutaneously with a cow colostrum polypeptide (CP) in a doze of 1 mg per g of body weight before the irradiation and daily after the irradiation during 4 days. In irradiated rat liver nuclei injected with CP the lipid peroxide oxidation was restored. At 90th day after the irradiation the production of dienes and dieneketones in liver nuclei oscillated in normal limits. The structure and cytochrome-c-oxidase activity of the nuclei was restored to 60-90th day after the irradiation.

[The immunochemical demonstration of high-molecular proteins in the nuclear matrix of tumor cells]

For characterization of a high molecular-weight protein group prevailing in the tumor nuclear matrix, monoclonal antibodies to MAP-like protein p260 and to fibronectin were used. Immunoperoxidase reaction in Western blots of nuclear matrix electrophoregrams revealed protein p260 both in normal liver and hepatomas 27 and 22a while fibronectin was found in hepatomas, but absent in the normal liver. Immunoelectron microscopy with gold-conjugated antibodies showed p260 to be uniformly spread in the nuclei while fibronectin was localized mostly at the periphery of the tumour nuclei.

[Effects of gamma irradiation on biosynthesis of nuclear matrix proteins of the liver in pregnant rats and their embryos]

A study was made of the incorporation of 35S-methionine into nuclear matrix proteins of hepatic cells of pregnant rats and their embryos subjected to single gamma-irradiation (60Co, 1 and 2 Gy, 0.0233 Gy/s) on days 3, 13 and 17 of pregnancy and embryogenesis. On day 21 of pregnancy and embryogenesis a decrease in the rate of incorporation of 35S-methionine into nuclear matrix proteins was shown to be a function of radiation dose and time of pregnancy and embryogenesis on the moment of exposure.

[Electron microscopic characteristics and polypeptide composition of the nuclear matrix of liver cells in mice with autoimmune disease]

A study was made of the ultrastructure and polypeptide composition of liver cell nuclear matrix of F1NZB/NZW hybrid mice imitating human systemic Lupus erythematosus. Electron microscopy reveals enlargement in fibrous lamina diameter and increase in pore complex density up to the age of 8-9 months. In the terminal stages of the disease (12-13 months of age) a gradual attenuation of the intranuclear matrix and disappearance of pore complexes is observed along with a segregation and subsequent fragmentation of residual nucleoli which results eventually in the general degradation of the nuclear matrix. 30-35 polypeptide bands with molecular weight from 200 to 10 kD are revealed in polyacrylamide gel electrophoresis of the liver cell nuclear matrix of hybrid mice. Several protein bands in the high molecular weight region of 200-150 kD are strongly enhanced, and a triplet with molecular weight 70-60 kD is distinctly visible. The results obtained are interpreted as an indication of a protecting cellular reaction against antinuclear autoantibodies in the earlier stages, and a degradation of the nuclear matrix in terminal stages of the disease. It is supposed that the electron microscopic and electrophoretic patterns of the nuclear matrix indicate an accumulation of collagenous proteins.

[DNA polymerase gamma in the cells of loach embryos localized in mitochondria]

The homogenate of loach (Misgurnus fossilis) embryonic cells was fractionated by differential centrifugation into fractions, in which the activities of DNA polymerases alpha and gamma were measured. About half of the total alpha-polymerase activity was retained in the postmicrosomal supernatant. The activity of gamma-polymerase in the supernatant did not exceed 2% of the total activity. The specific activity of gamma-polymerase was maximal in the mitochondrial pellet. The enzyme activity in the nuclear pellet was proportional to the activity of mitochondrial enzymes, cytochrome oxidase and KCN-insensitive superoxide dismutase. The nuclei were separated from gamma-polymerase-containing fraction by ultracentrifugation in a 10-50% sucrose density gradient. The material of this fraction was identical to the mitochondria in terms of buoyant density, morphology and enzymatic properties. Thus, in loach embryos the fraction of gamma-polymerase associated with the nuclei is absent; the total gamma-polymerase activity is localized in the mitochondria.

Granules 25-30 nm in diameter: basic constituent of the nuclear matrix, chromosome scaffold, and nuclear envelope

Rat liver nuclear matrix and similar structures derived from isolated Chironomus polytene chromosomes, nuclear envelopes, and intranuclear bodies of frog late oocytes (the karyospheres) were studied by electron microscopy with platinum shadowing and negative staining. We have shown that the treatment of whole nuclei, nuclear envelopes, polytene chromosomes, or karyospheres with nonionic detergent, high salt, and RNase and DNase followed by dilute alkali or hyaluronidase digestion reveals numerous rather uniform granules 25-30 nm in diameter. With omission of the nucleases the granules appear to be associated with DNA strands mostly organized in loops. Many granules form clusters and are arranged in linear or arch-like aggregates or cycles resembling the pore complexes. We suppose that these spherical bodies constitute a basic component of the nuclear matrix, chromosome scaffold, and nuclear envelope and are bound together by hyaluronic acid or some similar glycosaminoglycan.

[Karyosphere and nuclear envelope ultrastructure of oocytes of the common frog Rana temporaria after nuclease treatment and extraction of chromatin and alkali-soluble proteins]

The late oocyte karyosphere of Rana temporaria consists mainly of fibrillar nucleoli and micronucleoli, Fibrillar material containing the pore complexes (pseudomembranes) and modified synaptonemal complexes. Nuclease treatment of the karyosphere reveals regularly repeating bands in the nuclei and micronuclei, the fibrillar material associated with the nuclei being attenuated. After a subsequent treatment with DNase-1, RNase A and 1.5 M Nacl and karyosphere is disintegrated to involve remains of extracted nucleoli and fibrillar material containing pore complexes. 0.025 N NaOH extracted the bulk of the karyosphere and left only the islets if fibrillar material. The nuclear envelope proved to be far more stable to the above treatments. It retained its structure and was loosened partly only after 1.5 M NaCl or 0.025 N NaOH extraction, the pore complexes disappearing only after alkaline extraction. It is assumed that the karyosphere represents a skeletal structure (matrix) of the oocyte nucleus.

[Protein composition and electron microscopy of the residual protein fractions of cell nuclei of certain normal organs and tumors of rats]

A marked difference in polypeptide pattern and electron micrographs of the nuclear residual protein fraction between normal tissues /liver, kidney, spleen/ and tumors /hepatoma 27, Jensen and Yoshida sarcomas/ is revealed. While in normal tissues the polypeptides with molecular weight lower than 26 KD constituted about one half of the total residual protein, in tumors the polypeptides with molecular weight exceeding 100 KD were markedly prevailing. In electron micrographs the uniform filaments with a diameter of 4-5 nm, and periodical structure represented the bulk of the preparation from normal liver, while in the case of hepatoma 27 an amorphous granulated material was predominating.