A fetal protein in chromatin of Novikoff hepatoma and Walker 256 carcinosarcoma tumors that is absent from normal and regenerating rat liver

Antigenic Proteins of Nucleolar Chromatin of Novikoff Hepatoma Ascites Cells

Nucleolar chromatin of Novikoff hepatoma ascites cells contains an antigen (no-Ag1) detected with antinucleolar antibodies by the immunodiffusion technique. This antigen was distinguished from the previously reported nuclear chromatin antigen NAg-1 (19) by the findings that tumor nucleolar antibodies which formed immunoprecipitin bands with no-Ag1 did not do so with NAg-1 and that tumor cytosol, which contains NAg-1, formed immunoprecipitin bands with tumor chromatin antibodies but not with antibodies to tumor nucleoli. Tumor nucleolar chromatin contains both NAg-1 and no-Ag1, but only no-Ag1 formed bands with tumor nucleolar antibodies. no-Ag1 is a component of tumor nucleolar chromatin that was not soluble in 0.075 M NaCl - 0.025 M EDTA, pH 8, and only slightly soluble in 0.01 M Tris-HCl, pH 8. no-Ag1 was not found in liver nucleoli. Antibodies to liver nucleoli formed immunoprecipitin bands with liver nucleolar antigens but none were confluent with those formed between tumor nucleolar antibodies and antigens of tumor nucleolar chromatin. Absorption of the tumor nucleolar antibodies with whole tumor cells or whole liver pressate did not alter band formation with no-Ag1. Three antigens in liver nucleoli were not found in tumor nucleoli.

Fucosylated glycoproteins in Chinese hamster metaphase chromosomes

Distribution of fucosylated proteins in Chinese hamster metaphase chromosomes was studied with a fluorescein isothiocyanate conjugated monofucosyl-specific lectin, Ulex europaeus agglutinin I (UEA I). In situ binding of UEA I showed that fucosylated chromosomal proteins are preferentially localized to two internal structural domains of metaphase chromosomes: the helically coiled substructure of chromatids, and the Q-band regions. Corresponding proteins were identified in Western blots of isolated metaphase chromosomes. Several proteins with molecular weights ranging from 33 to 195 kD were recognized by UEA I. These data suggest that a subset of chromosomal proteins are fucosylated; they may have a role in the structural organization of chromosomes.

LYAR, a novel nucleolar protein with zinc finger DNA-binding motifs, is involved in cell growth regulation

A cDNA encoding a novel zinc finger protein has been isolated from a mouse T-cell leukemia line on the basis of its expression of a Ly-1 epitope in a lambda gt11 library. The putative gene was mapped on mouse chromosome 1, closely linked to Idh-1, but not linked to the Ly-1 (CD5) gene. The cDNA is therefore named Ly-1 antibody reactive clone (LYAR). The putative polypeptide encoded by the cDNA consists of 388 amino acids with a zinc finger motif and three copies of nuclear localization signals. Antibodies raised against a LYAR fusion protein reacted with a protein of 45 kD on Western blots and by immunoprecipitation. Immunolocalization indicated that LYAR was present predominantly in the nucleoli. The LYAR mRNA was not detected in brain, thymus, bone marrow, liver, heart, and muscle. Low levels of LYAR mRNA were detected in kidney and spleen. However, the LYAR gene was expressed at very high levels in immature spermatocytes in testis. The LYAR mRNA is present at high levels in early embryos and preferentially in fetal liver and fetal thymus. A number of B- and T-cell leukemic lines expressed LYAR at high levels, although it was not detectable in bone marrow and thymus. During radiation-induced T-cell leukemogenesis, high levels of LYAR were expressed in preleukemic thymocytes and in acute T leukemia cells. Fibroblast cells overexpressing the LYAR cDNA from a retrovirus vector, though not phenotypically transformed in vitro, had increased ability to form tumors in nu/nu mice. Therefore, LYAR may function as a novel nucleolar oncoprotein to regulate cell growth.

Preferential association of glycoproteins to the euchromatin regions of cross-fractured nuclei is revealed by fracture-label

We used fracture-label to establish ultrastructural localization of glycoproteins in cross-fractured nuclei of duodenal columnar and exocrine pancreatic cells. Mannose residues were detected in cell nuclei by labeling freeze-fractured tissues with concanavalin A-horseradish peroxidase X colloidal gold (Con A-HRP X CG) or direct concanavalin A X colloidal gold (Con A X CG); fucose residues were detected with Ulex Europaeus I X colloidal gold (UEA I X CG) markers. Areas of the three main intranuclear compartments (euchromatin, heterochromatin, and nucleolus) exposed by freeze-fracture were determined by automated image analysis. Colloidal gold particles bound to each nuclear subcompartment were counted and the results expressed in number of colloidal gold particles per square micrometer +/- SEM. Duodenal and pancreatic tissues fractured and labeled with Con A-HRP X CG complex or direct Con A X CG conjugates showed that the vast majority of Con A binding sites was confined to euchromatin regions with only sparse labeling of the heterochromatin and nucleolus. UEA I labeling of duodenal columnar cells showed that colloidal gold particles were almost exclusively confined to cross-fractured areas where euchromatin is exposed. Trypsinization of the fractured tissues before labeling with Con A and UEA I abolished 95-100% of the original label. Our results show that, within the nucleoplasm, mannose and fucose are residues of glycoproteins preferentially located within the regions of euchromatin.

Antibodies directed against guanylic acid and guanosine are nucleolus specific probes

Purified antibodies against guanylic acid and guanosine binding to RNA at guanosine residues were used to probe human lymphocyte preparations by indirect immunofluorescence. Neither antibody gave any banding pattern with metaphase chromosomes but both showed binding to specific sites in the interphase nuclei. Evidence presented indicates that these sites are guanosine residues on rDNA transcripts at the nucleolar organizer regions.

Age-related changes of the pattern of non-histone proteins in active and condensed fractions of mouse liver chromatin and hepatocarcinoma

Electrophoretic analysis of histones and non-histone acid-soluble proteins in active (nuclease sensitive) and inactive chromatin from liver of young and old CBA mice and in age-related hepatocarcinomas showed a higher ratio of NHP:histones in active chromatin in old cells. Some liver- and hepatoma-specific fractions of non-histone proteins have been identified as chromatin matrix proteins.

Interactions of U1 RNP with heterogeneous nuclear RNA in rat Novikoff hepatoma nuclei

The nature of the association of U1 RNA with rapidly sedimenting RNP structures in rat hepatoma nuclei was investigated. The effects of salt and proteinase K treatment on the stability of this 'bound' form of U1 RNA were studied using sucrose density gradient analyses. Quantitation of the amount of U1 RNA remaining associated with large structures after treatment was used to assess the relative contribution of protein-protein (and protein-RNA) versus RNA-RNA interactions. Forty-eight percent of the total nuclear U1 RNA released by sonication was found in a 'bound' form when the sonicate was centrifuged through gradients containing 50 mM NaCl. Fifty percent of this 'bound' U1 RNA remained associated with rapidly sedimenting RNPs when the NaCl concentration was raised to 500 mM. To assess the contribution of protein independent interactions, large RNPs were completely deproteinized and their RNA moieties were then recentrifuged on gradients. By this analysis, 27% of the U1 RNA originally 'bound' to hnRNPs was associated with rapidly sedimenting (greater than 30 S) RNA (at 50 mM NaCl) suggesting their association by RNA-RNA hydrogen bonds. When the concentration of NaCl was 500 mM, 31% of the U1 RNA was associated with large RNA. Hence, approximately 30% of the U1 RNA molecules originally 'bound' (or about 15% of the total nuclear U1 RNA) were found to be associated by RNA-RNA hydrogen bonds while the remainder of the binding of U1 RNP to hnRNP was by protein-protein and/or protein-RNA interactions.

Enzyme-linked immunosorbent assay for use with nuclear protein-DNA complex antigens

An enzyme-linked immunosorbent assay (ELISA) was developed for identification and quantification of nuclear antigens (nonhistone protein-DNA complexes from chromatin). Until now, the complement fixation assay has been the only immunoassay routinely applied to nonhistone protein-DNA complexes. The ELISA is considerably more sensitive than the micro-complement fixation test for assaying the immunospecificity of nuclear protein-DNA complexes. Dilutions of rabbit antisera as great as 1:6400 could be used to detect nanogram quantities of antigen, chicken reticulocyte chromatin or dehistonized rat liver chromatin.

Identification of cytosolic antigens from GW-39 adenocarcinoma cells by crossed immunoelectrophoresis and immunofluorescence

Rabbits were immunized with a cytosolic fraction prepared from human adenocarcinoma cells of the colon (GW-39). The antibodies obtained were analyzed using crossed immunoelectrophoresis and were found to precipitate 23 distinct antigens in the cytosolic fraction from colon tumor cells. After preabsorption with human serum and plasma as well as acetone powders prepared from 2 normal human tissues and 4 normal hamster tissues, 1 major immunodominant cytosol antigen (CA-3) and two less intense immunoprecipitin peaks (CA-1 and CA-5) remained detectable by the crossed immunoelectrophoretic method. The preabsorptions with normal tissues were sufficiently complete to remove anti-carcinoembryonic antigen antibodies and showed that antigens CA-1, CA-3 and CA-5 are immunologically distinct from carcinoembryonic antigen. Indirect immunofluorescence localization studies with preabsorbed anti-cytosol antibodies and FITC-conjugated second antibody showed that these antigens were expressed in the cytoplasm and at the cell surface in several human colon tumor cell lines, their subclones and in primary colon tumor specimens.

The characterization of non-histone proteins whose amounts increase in chromatin from mouse hepatocarcinomas

A fraction containing liver- and hepatoma-specific non-histone proteins has been isolated from the chromatin of mice. Amino acid analysis of this fraction shows that it contains 16 mol of glutamic acid, 10 mol aspartic acid, 7 mol of both arginine and lysine per 100 mol and contains no cysteine or tyrosine. The proteins in this fraction are strongly associated with DNA and are co-extracted with histones from chromatin with 0.25 M HCl. In chromatin from age-related hepatomas, the amount of this fraction increased six-fold. This increase in concentrations of these chromatin proteins may be associated with changes of chromatin structure necessary to initiate malignant growth in liver cells.

Evidence of the mannosylation of a non-histone protein in monkey liver chromatin

Mannose is incorporated in monkey liver chromatin by the means of a nuclear membrane mannosyltransferase. 14C-labelled chromatin is dissociated either by sulfuric acid or 6 M urea and 0.4 M GuCl. The fractions then enriched in non-histone 14C-labelled proteins are excluded from Ultro-gel AcA 202, their analysis in SDS-polyacrylamide gel electrophoresis shows that radioactivity fits with one major protein band, confirming the presence of at least a non-histone protein labelled with mannose in monkey liver chromatin, with an apparent molecular weight of 13,000.

Isolation and partial characterization of a nuclear antigen (68/6.3) from the Namalwa cell line (a Burkitt lymphoma)

A nuclear antigen was purified from the 0.01 M Tris-HCl/pH8 extract of nuclei of the Burkitt tumor Namalwa cell line to electrophoretic homogeneity by DEAE cellulose chromatography, affinity chromatography, and preparative isoelectric focusing. The yield of antigens was 0.02% of the nuclear 0.01 M Tris-HCl/pH8 extract. On two-dimensional gel electrophoresis, the major antigen separated into two adjacent protein spots with molecular weights of 68,000 and an approximate pI of 6.3 (68/6.3 A and 68/6.3 B). A minor antigen had a molecular weight of 61,000 and pI of 6.0 (61/6.0). Fourteen 125I-labeled peptides were obtained from the tryptic digest of the major antigen (68/6.3 A and 68/6.3 B). The amino-acid composition analysis of the purified antigens indicated that the amino acids in the highest content were glycine (15%), glutamic acid (11.6%), and serine (9%); the ratio of acidic to basic amino acids was 1.95. In studies on nucleolytic activity, the purified antigen produced a single-stranded and then a double-stranded cleavage of PM 2 and pBR 322 DNA. This antigen is the first purified nuclear antigen that reacts with the HeLa-specific nucleolar antibodies.

New dimensions in the biology of cancer

A common thread interwoven throughout the literature of cancer biology is a wide-ranging abnormality of gene regulation, manifested by misprogramming of protein synthesis. This phenomenon encompasses virtually every means of identification of proteins, including antigens, hormones, growth factors, membrane components, and enzymes. Studies by the author and others of the activities of enzymes existing in multiple forms (termed isozymes) in a series of rat hepatomas ranging widely in growth rate, degree of differentiation, and other phenotypic properties has extended this concept and added to it a dimension of functional significance. Isozymes that are in high activity in adult liver and that are geared kinetically to catalyze specific hepatic functions are lost in varying degrees and generally depend on the growth rate and degree of differentiation. In fast growing, poorly differentiated hepatomas, these are replaced by high activities of isozymes that are normally low or absent in adult liver. In many instances, the isozymes that are expressed in poorly differentiated hepatomas are present also in fetal liver, thus pointing to reactivation of genes that were active in the fetus but were inactivated during normal embryonic development. The loss of isozymes that are under rigid host endocrine control, as well as other proteins that maintain the differentiated state, and the re-activation of genes coding for fetal or ectopic proteins are probably crucial factors in the initiation and maintenance of cellular proliferation.

Antigenic changes in nuclear chromatin in 1,2-dimethylhydrazine-induced colon carcinogenesis

Chromosomal nonhistone protein-DNA complexes prepared from rat colon adenocarcinoma were used to produce tumor specific antisera in rabbits. The antisera reacted specifically in complement fixation tests with chromatins isolated from rat colon tumor and not with those from a number of other rodent tumors and normal tissues, including normal rat colon epithelial cells. Tumor specificity of this antisera was also demonstrated by their cross reactivity with human and mouse colon adenocarcinomas. Immunohistochemical localization of the antigens by the horseradish peroxidase bridge technique demonstrated their presence in the nuclei. The changes in the immunospecificity of the nuclear antigens in chromatin were studied in colon of rats treated with 1,2-dimethylhydrazine. A significant change in the immunospecificity of the chromatin occurred as early as the fourth week after 1,2-dimethylhydrazine treatment was begun.

Cell-specific antigens in chicken erythroid nuclei: species specificity

Antisera raised to dehistonized chicken reticulocyte chromatin were tested for their cell and species specificity. Quantitative microcomplement fixation and immunohistochemical localization revealed the presence in chromatin of erythroid cell-specific nonhistone protein antigen(s). The antigenic specificity was shown to depend on the association of the antigenic protein(s) with deoxyribonucleic acid (DNA). Although the antisera were exceptionally cell specific, they cross-reacted with erythroid cells of other avian species. The extent of cross-reactivity was found to approximate the phylogenetic distances of the tested avian species. Erythroid cells from fish and amphibians were not reactive. Reconstitution experiments of partially purified chicken reticulocyte chromosomal nonhistone protein antigens with DNAs isolated from several vertebrate species showed that the species specificity of the antigenic complexes is determined principally by the species origin of the nonhistone proteins. Our results show that a cell-specific chromosomal nonhistone protein(s) has undergone evolutionary change and the relative immunological differences are consistent with the accepted phylogenetic distances of the species examined.

Subcellular localization of DNA-binding protein BA by immunofluorescence and immunoelectron microscopy

Nonhistone protein BA has been shown to decrease in amount in the chromatin of growth- stimulated normal rat liver (Yeoman et al. 1975. Cancer Res. 35:1249-1255) and in mitogen-stimulated normal human lymphocytes (Yeoman et al. 1976. Exp. Cell Res. 100:47- 55.). Subsequently, protein BA was purified and was shown to prefer to bind to double- stranded A-T-rich DNAs (Catino et al. 1978. Biochemistry. 17:983-987.). Immunization of rabbits with highly purified protein BA has resulted in the production of a specific antibody. A specific immunoreactivity for chromosomal protein BA has been demonstrated by immunoelectrophoresis and double antibody immunoprecipitation analysis with rabbit anti-BA immunoglobulin and IgG fractions. Light microscope examination of normal rat liver crysections by the indirect immunofluorescence procedure has demonstrated a cytoplasmic as well as a nuclear localization for protein BA with a pronounced perinucleolar fluorescence. Immunoelectron microscopy employing the peroxidase antiperoxidase method of antigen localization has confirmed the immunofluorescence data and has show a heterochromatin localization for protein BA. The relationship of the localization of protein BA to gene control in quiescent cells or to configurations of heterochromatin as well as the marked reduction in the amounts of protein BA which occur in stimulated growth states remains to be defined.

Binding of Lens culinaris lectin to sea urchin embryo chromatin

Lentin binds specifically to sea urchin embryo chromatin. This binding is saturable and inhibited by alpha-methyl-mannose. Scatchard plot analysis of the binding reaction suggests a single binding site.

Nucleolar antigen found in several human tumors but not in the nontumor tissues studied

Rabbit antibodies to nucleoli isolated from HeLa cells produced bright nucleolar fluorescence in HeLa cells by the indirect immunofluorescence technique. After absorption with fetal bovine serum and placental nuclei, the IgG still produced bright nucleolar fluorescence in 12 human tumor cells including HeLa, HEp-2, cultures of prostate and mammary carcinomas, the Goldenberg GW-39 colon tumor, and biopsy specimens of prostatic, adrenal cortical, thyroid, and squamous cell carcinomas, a hairy cell leukemia of the spleen, a hepatic metastasis of an adenocarcinoma of the colon, and an osteogenic sarcoma. Bright nucleolar fluorescence was not produced in nine nontumor human cells including biopsy specimens of bone marrow, kidney, placenta, thyroid, liver, and prostate, peripheral blood buffy coat, and cultures of normal skin fibroblasts. Nucleolar fluorescence with the absorbed IgG was prevented in HeLa cells by pretreatment of the cells with acid, base, and proteases but not by pretreatment with nucleases; absorption of this IgG with extracts of HeLa nucleoli prevented the nucleolor fluorescence in HeLa and other human tumor cells.

Two-dimensional polyacrylamide gel analysis on nuclear proteins from human tumor cell lines

Two-dimensional polyacrylamide gel electrophoretic analysis was carried out on HeLa, KB, ALL and GW-39 cell "Chromatin Fraction II" proteins. Of the many proteins found, most were visualized in earlier studies on rodent tumors and normal tissues. Of these the greater density of protein CP and the presence of protein CG' differentiates tumors from the nontumor tissues. In samples of normal and mitogen stimulated human lymphocytes, protein CG' was absent and protein CP was present in small amounts. Two-dimensional patterns of 0.4N H2SO4 soluble nuclear proteins showed elevated amounts of proteins C16-18 in the GS-39 cell patterns. Proteins Hu1, G1, G2, G3 and G5 were detected only in human cell nuclei. The increased density of staining for protein CP and the presence of CG' are potential biological markers for neoplastic cells.

Purification of nuclear antigens in Novikoff hepatoma

Nuclear antigen in Novikoff hepatoma chromatin was partially purified and characterized. As indicated by complement fixation assay, this antigen was present in chromatin of embryonic livers and several transplantable tumors. It was not detected in normal tissue chromatins of the same animals. For its immunological specificity this protein antigen (molecular weight 45,000-60,000) had to be complexed with DNA. Preliminary experiments indicate that specific nuclear protein antigens are also present in human tissues and spontaneous malignancies.

Antigenic differences in nuclear proteins of normal liver and hepatoma. Identification of a nuclear protein present in hepatocytes but absent in hepatoma cells

A nuclear antigen was detected in the mouse liver nonhistone protein fraction by using antibodies to whole liver cells. The antigen was purified to homogeneity from perchloric acid extracts of liver tissue. It gave a single band corresponding to tool wt 21,000 in sodium dodecyl sulfate gel electrophoresis. Amino acid and carbohydrate analysis showed predominance of the acidic amino acids, lack of proline, and absence of carbohydrate. Immunofluorescence staining of liver sections confirmed the nuclear localization of the antigen. Its tissue distribution was studied by using radioimmunoassay. Of the various tissues extracted for analysis, the liver contained the highest amounts of the antigen, about 1 mug/mg of solubilized liver protein. Other tissues examined showed 2-4 percent of the amount of antigen present in the liver. Two transplantable hepatomas in C3H/HeJ and C57L/J mice, respectively, and three spontaneous C3H hepatomas showed greatly decreased levels of the antigen compared to normal liver. The amount of antigen in hepatomas varied from nondetectable to 2 percent of the amount of antigen found in the livers of the mice. The antigen was also found in the blood. The antigen was found in high concentrations (up to 13 mg/ml) in the urine of normal mice. This suggests identity with the previously known mouse urinary protein (MUP). In addition to the extremely high urinary output, the properties found to be shared by MUP and the nuclear antigen included similar serum concentrations (2-60 mug/ml), a sex difference with lower values in females, same molecular size as determined by gel filtration, and immunological identity. The nuclear localization of MUP and its disappearance from hepatomas suggest that it may have an important regulatory function.