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At least 19 recordsLinked to original sources
PubMed1979

Comparative aspects of nuclear proteins and nuclear composition of cultivated embryonic, neonatal and neoplastic rat brain cells of glial origin.

Differences in nuclear composition and variations in the types of acid soluble nuclear proteins were identified when cultivated neoplastic and nontransformed rat brain cells were compared. HeLa S-3 cells were used as a biological reference in these studies. The nuclei of anaplastic glioma cells were found to contain more total nuclear protein and greater amounts of nuclear RNA, than the nuclei of nontransformed embryonic and neonatal rat brain cells. Densitometer profiles of samples developed by polyacrylamide gel electrophoresis indicated that all three major histone classes were present in the nuclei of the four different cell types examined. Each type of cell was grown in the presence of 3H-lysine or 3H-lysine plus 14C-arginine to further characterize both the histones and the acid soluble nonhistone proteins. Neoplastic and nontransformed cells contained similar quantities of histones H4, H3, H2A and H2B. In contrast, transformed cells were found to contain two dominant subspecies of lysine rich H1 histone, while only one histone H1 subcomponent was extracted from the nuclei of the embryonic and neonatal rat brain cells. Nuclei isolated from HeLa cells and anaplastic glioma cells also contained increased varieties and larger quantities of acid soluble nonhistone nuclear proteins.

Animals↗
PubMed1977

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.

Animals↗
PubMed1977

Adenosine 3',5'-monophosphate-dependent protein kinases of myocardial non-histone nuclear proteins.

Myocardial acidic non-histone nuclear proteins (NHPs) contain endogenous protein kinase activity. Phosphocellulose chromatography of purified NHPs identifies nine separate peaks of protein kinases which can phosphorylate both endogenous and exogenous substrates to a variable degree; endogenous NHPs are the best substrates. Cyclic AMP-stimulated protein kinase induced phosphorylation of endogenous and exogenous substrates; the extent of this stimulation varied according to the protein kinase fraction and substrate used. Cyclic AMP also enhanced NHP-induced stimulation of RNA polymerase activity. This enhancement was dependent on protein kinase-induced phosphorylation of NHPs since it was prevented by alkaline phosphatase pretreatment. It is concluded that nuclear protein kinases regulate myocardial RNA synthesis by enhancing phosphorylation of NHPs and that this regulation is under cyclic AMP control.

Adenosine Triphosphate↗
PubMedDate not supplied

Cytophotometry of feulgen-naphtol yellow S stained liver cells--a computerized method for the calculation of nuclear protein.

A computerized method was developed to calculate the nuclear protein content of Feulgen-Naphtol Yellow S stained liver cells from cytophotometric data. After two consecutive scannings at 570 nm (DNA) and 435 nm (protein), the nuclear localization and shape are defined and nuclear protein is calculated by a method which corrects for the nuclear-cytoplasmic overlap at the nuclear periphery. The results obtained by the procedure are highly reproducible and are in accordance with the results of biochemical determinations of nuclear and total cell protein reported by others.

Animals↗
PubMed1978

Purification of rat liver nuclear protein kinase NI.

Rat liver nuclear protein kinase NI, which appears in the flowthrough of DEAE-Sephadex columns, has been purified approximately 15,000-fold from soluble nuclear protein with yields of up to 10%. The method of purification involved chromatography of the DEAE-flowthrough protein successively on phosvitin-Sepharose and casein-Sepharose followed by rechromatography on phosvitin-Sepharose. The purified enzyme has an s20,w and molecular weight of 3.7 and 47,000, respectively, as determined by sucrose density gradient centrifugation in 0.4 M NaCl. A similar molecular weight of 42,000 was determined by gel filtration using Sephadex G-100. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed a single polypeptide with a molecular weight of 25,000. Protein kinase NI therefore consists of a dimer of two identical subunits. Protein kinase NI exhibits maximal activity on casein substrate and is not stimulated by 10(-5) to 10(-4) M cAMP or cGMP when either casein or histone H2b is used as a substrate.

Animals↗
PubMed1975

Nuclear proteins of rat liver and of an aminoazo-dye-induced hepatoma.

Nuclear proteins of rat liver and rat ascites hepatoma were fractionated by extraction in solutions of different salt concentration and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The difference between the electrophorograms of the different fractions of nuclear proteins isolated from liver and from hepatoma was found in the bands which have the same electrophoretic mobility as the main proteins of informofers and are extracted from nuclei at salt concentrations which extract informofers. These changes in the electrophoretic patterns of proteins with the solubility and mobility of the proteins of informofers could be related to the defective processing of heterogeneous nuclear RNA in the hepatoma. In addition the identity of electrophorograms of nuclear proteins isolated from liver and from hepatoma and the identity of most bands in the electrophorograms of nuclear proteins which are soluble in 0.35 M NaCl and chromosomal proteins which are not soluble at this salt concentration support the notion that these nonhistone nuclear proteins which can be identified as the major bands in electrophorograms of chromosomal proteins are not the specific regulators of gene expression.

Animals↗
PubMed1977

Cytoplasmic and nuclear protein kinases during the cell cycle.

Nuclear and cytoplasmic protein kinases were measured during the traverse of synchronous CHO cultures through G1 into S phase. Cells were synchronized by selective detachment of cells blocked in metaphase using colcemid. Nuclei were isolated and the protein kinases extracted from the nuclear preparation with 0.6 M NaCl. This procedure solubilized greater than 90% of the total protein kinase activity present in the nuclear preparation. DEAE chromatography of this extract showed 5 apparently different ionic forms of nuclear protein kinases. The nuclear protein kinases preferred casein and phosvitin to histone as substrates and were cyclic AMP-independent. Nuclear protein kinase activities increased greater than two-fold, when expressed as units of activity per cell nucleus, during G1 phase traverse, concomitant with a 70% increase in nuclear non-histone proteins (those soluble in 0.6 M NaCl). This resulted in only a 40% increase in the specific activities (units/microgram protein in 0.6 M NaCl extractable nuclear fraction) of these enzymes as cells progressed through G1 into S phase. This was in contrast to cytoplasmic cyclic AMP-dependent protein kinase activities which also increased two-fold during progression through G1 phase while total cellular protein increased less than 20%. Activation of, as well as synthesis of, cyclic AMP-dependent cytoplasmic protein kinases during G1 phase suggests a regulatory mechanism for precise temporal phosphorylation, whereas the constant specific activity in nuclear kinases during cell cycle is more compatible with the maintenance of bulk phosphorylation processes in the nucleus.

Cell Cycle↗
PubMed1977

[Nuclear proteins and DNA in the myocardial myocytes in compensatory cardiac hypertrophy].

Using cytophotometry, the amount of DNA, total nuclear proteins and of histones were studied in the myocardial cells during days 21--36 of experimental compensatory hypertrophy of the heart (in rats). The enlargement of myocardial nuclei during the cardial hyperfunction was accompanied by accumulation of total nuclear protein, in particular, the histone fraction, without distinct changes in DNA. Analysis of correlations between nuclear proteins and DNA in the myocardial cells allows to reveal a delayed accumulation of histones in the big and gigantic nuclei, with a superfluous increase in non-histone nuclear proteins. In middle-sized nuclei, non-histone proteins have little changes against intensive accumulation of histones.

Animals↗
PubMed1975

Nuclear protein changes in rat hepatomas correlating with growth rate.

The nature of nuclear proteins that are soluble in 8 M urea-50 mM phosphate, pH 7.6, was compared in rat liver and Morris hepatomas, Isoelectric focusing, using carrier ampholytes for a pH gradient of 3.5 to 10, indicated that with increasing growth rate of the hepatomas there was a progressive tendency for a decrease in nonhistone nuclear proteins with isoelectric points in the range 7.5 to 8.9 and an increase in the range 5.1 to 6.7. Studies on the influence of time on the pH gradient revealed that a nonuniform drift provided a better resolution of the pH range 7.5 to 8.9 at 7 hr than at 24 hr, while the latter time for electrofocusing gave an improved resolution of the pH range 5.1 to 6.7 Polyarcylamide gel electrophoresis in a urea-acetic acid system showed that 8 M urea-50 mM phosphate; pH 7.6 extracted a small part of the histones from nuclei of both liver and hepatomas. There was less extraction of histones from the hepatoma nuclei, especially in two rapidly growing hepatomas with the most notable difference being seen in the lysine-rich H1 histone. The results suggested that in addition to qualitative or quantitative changes in nonhistone nuclear proteins in liver cancer there are alterations in the binding of histones to chromatin.

Acetates↗
PubMed1979

Cytoplasmic and nuclear protein synthesis in preimplantation mouse embryos.

Cytoplasmic and nuclear proteins synthesized by mouse embryos at different stages of preimplantation development were analyzed by two-dimensional polyacrylamide gel electrophoresis. Several nuclear-specific proteins (i.e. proteins more abundant in the nucleus than in the cytoplasm) and numerous cytoplasmic-specific proteins were observed. The trends of changes in the nuclear and cytoplasmic protein synthesis are similar. Moderate changes occur between the unfertilized egg and the zygote. Striking changes characterized by the disappearance of numerous major oocyte-specific proteins and the appearance of a large number of new, stage-specific proteins occur between the zygote and the 4- to 8-cell stages. In contrast, between the 4- and 8-cell and early blastocyst periods, only a few new proteins appear, and a small number of oocyte-specific or other stage-specific proteins disappear. Minor differences in protein synthesis were observed between the trophoblast and inner cell mass.

Animals↗
PubMed1975

Fractionation of nuclei and analysis of nuclear proteins of rat liver and Morris hepatoma 7777.

The contributions of nuclear populations to the total profile of nuclear proteins in a tissue were examined in normal rat liver and Morris hepatoma 7777. Comparison by sodium dodecyl sulfate polyacrylamide gel electrophoresis of phenol-soluble nuclear proteins from tumor and control liver revealed additional proteins of molecular weight 60,000, 100,00, and 135,000 and the loss of proteins of about 45,000 and 55,000 in the tumor. Subfractionation of liver nuclei on a 30 to 50% sucrose gradient yielded three nuclear classes with nearly identical complements of the phenol-soluble proteins. Similar fractionation performed on the hepatoma nuclei also produced three nuclear populations. In the hepatoma nuclei, several differences in the phenol-soluble proteins were found between the minor, slowly sedimenting nuclear fraction, and the two major fractions, while the two latter fractions were very similar in their protein composition. Histones derived from both tissues were also compared electrophoretically, indicating a decrease in the concentration of histone H1(0)in all nuclear classes derived from the tumor.

Animals↗
PubMed1979

Nuclear protein modification and chromatin substructure. 3. Relationship between poly(adenosine diphosphate) ribosylation and different functional forms of chromatin.

The relationship between poly(adenosine diphosphate) ribosylation of nuclear proteins and functionally different forms of chromatin from mid-S-phase HeLa nuclei was investigated. The major observations emerging from this study were that unique nonhistone proteins were modified in mid-S-phase HeLa nuclei. The major acceptor for poly(adenosine diphosphate-ribose) [poly(ADP-Rib)] was an internucleosomal nonhistone protein (protein C; 125 000 molecular weight). Histones H3, H1, H2b, and H2a but not H4 were ADP-ribosylated in S-phase nuclei. Chromatin fragments preferentially released by micrococcal nuclease were enriched in nonhistone proteins, poly(ADP)-ribosylated nuclear proteins, poly(ADP-Rib) polymerase activity and nascent DNA from the DNA replicating fork. In extended forms of chromatin, contiguous to the DNA replicating fork, poly(ADP-Rib) polymerase was maximally active. However, in chromatin distal to the replicating fork (i.e., more condensed structures), nucleosomal histones and histone H1 were not significantly ADP-ribosylated, and poly(ADP-Rib) polymerase activity was depressed two- to threefold. The data suggest that a subset of nucleosomes in extended regions of chromatin is subject to extensive ADP ribosylation.

Cell Nucleus↗
PubMed2025

O-GlcNAcylation of nuclear proteins in the mouse liver exhibit daily oscillations that are influenced by meal timing.

The liver circadian clock and hepatic transcriptome are highly responsive to metabolic signals generated from feeding-fasting rhythm. Previous studies have identified a number of nutrient-sensitive signaling pathways that could interpret metabolic input to regulate rhythmic hepatic biology. Here, we investigated the role of O-GlcNAcylation, a nutrient-sensitive post-translational modification (PTM) in mediating metabolic regulation of rhythmic biology in the liver. We observe daily oscillation of global nuclear protein O-GlcNAcylation in the liver of mice subjected to night-restricted feeding (NRF) using label-free global O-GlcNAc proteomics. Additional site-specific O-GlcNAc analysis by tandem mass tag mass spectrometry further supports temporal differences in O-GlcNAcylation by revealing day-night differences. Proteins involved in gene expression are enriched among rhythmically O-GlcNAcylated proteins, suggesting rhythmic O-GlcNAcylation may directly regulate the hepatic transcriptome. We show that rhythmic O-GlcNAcylation can also indirectly modulate nuclear proteins by interacting with phosphorylation. Several proteins harboring O-GlcNAcylation-phosphorylation interplay motif exhibit rhythmic O-GlcNAcylation and phosphorylation. Specifically, we show that O-GlcNAcylation occurs at a phospho-degron of a key circadian transcriptional activator, circadian locomotor output cycles kaput (CLOCK), thus regulating its stability and transcriptional output. Finally, we report that day-restricted feeding (DRF) in the nocturnal mouse significantly alters O-GlcNAcylation pattern. Whereas global O-GlcNAcylation analysis indicates dampening of global O-GlcNAcylation rhythm in mice fed under DRF, site-specific analysis reveals differential responses of O-GlcNAc sites when timing of food intake is altered. Notably, a substantial number of O-GlcNAcylation sites exhibit inverted day-night profiles when mice are subjected to DRF. This suggests the dysregulation of daily nuclear protein O-GlcNAcylation rhythm may contribute to the disruption in liver transcriptome previously observed in DRF condition. In summary, our results provide new mechanistic insights into metabolic regulation of hepatic transcriptional regulators via interplay between O-GlcNAcylation and phosphorylation and shed light on the deleterious effects of improper mealtimes.

Animals↗
PubMed1979

Spermine-induced variations in the adenosine 5'-diphosphate ribosylation patterns of nuclear proteins from rat liver and hepatoma.

Rat liver and hepatoma nuclei were incubated in vitro with [3H]nicotinamide adenine dinucleotide to allow synthesis of a polymer of adenosine diphosphoribose subunits joined in an 1',2' ribose-ribose linkage. The addition of 1 mM spermine altered the adenosine 5'-diphosphate (ADP) ribosylation patterns of nuclear proteins in hepatoma, host liver, and regenerating liver. Spermine-treated nuclei showed a greater incorporation of ADP-ribose into H1 histones and nonhistone nuclear proteins with isoelectric points between pH 3.0 and 6.0 when separated on polyacrylamide gels. Conversely, a large reduction in ADP ribosylation was seen in core histones (H2A, H2B, and H3) from the same nuclei. The proportion of ADP-ribose incorporated into histones was reduced in the nuclei from proliferating cells relative to their respective control livers. These results imply that polyamines, which are higher in concentration in rapidly dividing cells, may elicit a regulatory function by causing the preferential ADP ribosylation of H1 histones, as well as the more acidic of the nuclear proteins.

Adenosine Diphosphate Sugars↗
PubMed1975

Changes in nuclear proteins of rat testis cells separated by velocity sedimentation.

The technique of velocity sedimentation at unit gravity has been used to separate rat testis cell suspensions into fractions enriched in particular cell types. Changes in the nuclear proteins from the various fractions have been characterized by polyacrylamide gel electrophoresis, and correlated with the changing morphology of the nucleus during spermatogenesis. The most striking alterations in both protein composition and nuclear morphology occur during spermatid maturation as both histone and non-histone proteins are replaced by highly basic, low molecular weight, spermatidal proteins. This replacement process is accompanied by a quantitative reduction in both histone and non-histone proteins. The synthesis of at least three basic proteins has been identified with late stage spermatids. One of these proteins is a highly basic sperm-specific protein containing high levels of cyst(e)ine and arginine. A second protein synthesized in late stage spermatids is lysine rich, while the third protein contains cyst(e)ine and co-migrates with histone F2a1 on acid-urea polyacrylamide gels. The changes in protein composition of rat testis nuclei after irradiation or hypophysectomy reflect the resulting changes in the cellular composition of the testis. After selective elimination of the germinal cells by irradiation, the electrophoretic pattern of acid-soluble proteins from the testis is very similar to that of somatic tissue. Thus, the cellular specificity of nuclear proteins demonstrated here using cell separation techniques is also apparent following treatments which selectively alter the cellular composition of the testis.

Amino Acids↗