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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Histone acetate is hydrolyzed rapidly in logarithmically dividing hepatoma tissue culture cells (Jackson, V., Shires, A., Chalkley, R. and Granner, D.K. (1975) J. Biol. Chem. 250, 4856--4863). The phenomenon has been analyzed further in hepatoma tissue culture cells at various stages of the cell cycle, in stationary phase, and in the presence of actinomycin D. We also investigated the phenomenon in Tetrahymena pyriformis macronuclei, bovine thymocytes, and human foreskin fibroblasts. The data suggest that this highly metabolically active histone acetylation while altered in mitotic cells, is independent of the overall rate of cell division, and is only slightly sensitive to actinomycin D. Finally, we conclude that the same general phenomenon is found in both cancerous and normal cells and is apparently common to cells from various stages of the evolutionary scale.
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PMID:Comparative studies on highly metabolically active histone acetylation. 10 58

Proteinase associated with chromatin isolated from liver and hepatoma of rat is stimulated by salt, and, of the histone fractions, lysine-rich (F1) histone is preferentially degraded by this enzyme at an ionic strength comparable with that found in the nucleus. However, there appears to be no strict relationship between the activity of the proteinase and growth rates of hepatomas. Chromatin isolated from a fast-growing tumour, Ehrlich ascites carcinoma, shows no apparent proteinase activity in the presence of salt.
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PMID:Lack of relationship between activity of chromatin-bound proteinase and cell growth rates. 16 17

A group of chromosomal non-histone proteins with affinity for DNA (NP) was isolated from rat liver and Novikoff hepatoma. This fraction, which represents less than 5% of the total chromatin protein content, binds preferentially to unique, double-stranded sequences of fractionated homologous DNA. The interactions are strong at low ionic strength (Km = 6.7 X 10(-9) M) and decrease with rising salt concentration. Complexes of the NP protein fraction with homologous DNA are immunologically tissue-specific. As determined by microcomplement fixation, the NP proteins in Novikoff hepatoma are associated with the transcriptionally active, diffuse fraction of chromatin.
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PMID:Tissue-specific chromosomal non-histone protein interactions with DNA. 17 52

Circadian rhythms and cell cycles are endogenous self-sustained oscillations. They differ in several characteristics of the rhythmicity such as temperature dependency, reaction to external stimuli and the impact of protein synthesis. In multicellular organisms, the cell cycle very often is entrained by a circadian rhythm as has been analyzed in rats and mice, in particular. The same seems to hold true in cell cultures: Yoshida-ascites hepatoma cells, human embryonic fibroblasts, rat liver and rat hepatoma cells show circadian changes in the percentage of cells in G1-, S- and G2 + M-phases. The different phases within the cell cycle were determined by applying impulse cytophotometric methods. Some hypothetical mechanisms of entrainment of the cell cycle by circadian rhythms are discussed. Possible entrancing signals (Zeitgebers) are membrane and transport functions, cyclic nucleotides, nuclear non-histone proteins and their phosphorylation, and RNA synthesis. The maxima of the circadian rhythms of most of these functions in rat liver can be arranged in a certain temporal sequence.
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PMID:Circadian rhythm and cell cycle: possible entraining mechanisms. 17 64

The purpose of the experiments was to determine if changes in the post-transcriptional processing of RNA in the hepatoma also affect the low molecular weight nuclear RNA which is transcribed from families of related genes and associated with non-histone chromosomal proteins. Separation of non-histone chromosomal proteins on Sephadex G-200 into three fractions separated the low molecular weight RNA associated with these proteins into metabolically stable RNA firmly bound to the first eluted fractions of high molecular weight non-histone chromosomal proteins, and into a metabolically active RNA which is eluted with the third protein fraction and can be separated from the low molecular weight non-histone chromosomal proteins by chromatography on DEAE-Sephadex A 25 (fraction III RNA). In liver as well as in hepatoma, this fraction III RNA represents about 50% of the RNA associated with the non-histone chromosomal proteins. Fraction III RNA from both tissues has an approximate molecular weight of 13,000, is rich in guanylic acid, is lacking dihydropyrimidines and is copied from the repetitive sequences of DNA. The content of uridylic acid is much higher in fraction III RNA isolated from hepatoma than in the same RNA isolated from liver, and competitive hybridization has shown that hepatoma fraction III RNA contains not only new base sequences which are not present in liver fraction III RNA, but also lacks some sequences which are present in the liver RNA. The technique of RNA/DNA hybridization in the presence of competing RNA has shown that, in hepatoma, the cytoplasmic RNA competes with more than 60% of the fraction III RNA for the hybridization sites on repetitive DNA. No competition was found when liver cytoplasmic RNA was used. The low ratio of competing hepatoma cytoplasmic RNA or of liver or hepatoma nuclear RNA which is required to displace fraction III RNA from its hybridization with DNA indicates that this RNA is synthesized and in hepatoma is also released into the cytoplasm as a part of larger RNA molecules. The detection of the nucleotide sequences found in liver associated with non-histone chromosomal proteins in the cytoplasm of hepatoma cells is evidence for extensive disruption of the post-transcriptional control in hepatoma.
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PMID:RNA associated with non-histone chromosomal proteins in rat liver and in ascites hepatoma. 17 56

Smooth and rough endoplasmic reticulum from rat liver and hepatomas exhibited endogenous protein kinase activity independent of adenosine 3':5'-monophosphate. The phosphorylation of smooth membranes by this process was consistently higher than that of rough membranes. When histone was added along with the smooth endoplasmic reticulum, cyclic AMP stimulated protein phosphorylation. Analysis of membrane-phosphorylated proteins by gel electrophoresis showed 5 major phosphorylated bands with estimated molecular weights of 155 000, 62 000, 50 000, 46 000 and 43 000, whereas major bands having estimated molecular weights of 62 000, 50 000 and 43 000 were found in membranes of the smooth endoplasmic reticulum of the Morris hepatoma 5123 C. Since previous studies in this and other laboratories have demonstrated the similarity of the protein components of membranes of the endoplasmic reticulum of normal liver and hepatoma, our findings indicate an inability of the protein kinase of hepatoma intracellular membranes to phosphorylate protein species that are found in membranes of both liver and the neoplasm.
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PMID:Protein phosphorylation of the smooth and rough endoplasmic reticulum in normal and neoplastic liver of the rat. 18 Dec 47

Two-dimensional polyacrylamide gel electrophoresis shows that in nuclei of Novikoff hepatoma ascites cells there are approximately 75 proteins in the chromatin fraction soluble in 3 M NaCl:7 M urea. Dialysis of this fraction to an ionic strength of 0.15 produces a soluble fraction and a precipitate. The proteins in the soluble fraction have been reported to be active in gene control. Antibodies to the soluble fraction distribute diffusely throughout the nucleus, and antibodies to the precipitate localized primarily in the nucleolus and the nuclear ribonucleoprotein network. The nucleolar proteins differ from the extranucleolar proteins in antigenicity and labeling patterns. The development of methods for isolation, purification, and identification of nuclear proteins provided the opportunity for analysis of chromatin antigens in tumor cells. Utilizing two-dimensional preparative polyacrylamide gel techniques as well as conventional procedures, several nuclear proteins have been isolated in electrophoretically homogeneous states including protein A-24, a histone-like nonhistone protein; C-14, a protein that stimulates nucleolar RNA polymerase; and a chromatin antigen soluble in 3 M NaCl:7 M urea that remains soluble after dialysis to 0.15 M NaCl to precipitate the histones and the DNA. This antigen has been found in the chromatin of both the Novikoff hepatoma and the Walker 256 carcinosarcoma but not in the chromatin of either normal or regenerating liver. It is a nonhistone nuclear protein as indicated by its amino acid analysis in which the ratio of the number of acidic to basic amino acids is approximately 1.4. Further studies are in progress on the function and structure of this chromatin protein. As an approach to analysis of relative rates of synthesis of this antigen and otherproteins, the products of translation of messenger RNA of Novikoff hepatoma and normal liver are being analyzed by autoradiography of two-dimensional electrophoretic gels.
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PMID:Antigenically active nonhistone chromatin proteins in cancer cells. 18 49

1. The chemical composition of chromatins obtained from Buffalo rat liver and Morris hepatoma strain 5123 was investigated. 2. The presence of an additional subfraction within the very lysine-rich histone (fl) was states in both kinds of tissues. It amounted to about 8% and 5% of fl in rat liver and Morris hepatoma, respectively. 3. Nuclear phosphoproteins (phenol-soluble) from normal and tumour tissues in polyacrylamide gel in SDS showed some qualitative differences in the range of molecular weights of about 40 000 - 70 000 and over 100 000 daltons.
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PMID:Studies on histones and nuclear phosphoproteins of rat liver and Morris hepatoma. 18 36

The effects of exogenous proteins on the incorporation of [3H]-thymidine into DNA was studied in Novikoff hepatoma ascites cells incubated in Eagle's minimal essential medium. A liver cytosol fraction (8 mg protein/ml) caused approximately 80% inhibition of isotope incorporation. The inhibitory activity of cytosol fractions from Morris hepatomas 9618A2, 5123C, and 20 were inversely related to their growth rate. Under conditions in which there appeared to be a density dependent inhibition of growth, a mean 10-20% stimulation of isotope incorporation was observed after addition of total calf thymus histones and individual fractions in the concentration range of 100-400 microgram/ml. In experiments with lower cell concentrations, a 60% or greater increase in [3H]-thymidine incorporation could be obtained with total calf thymus histone and with F1 and arginine-rich histones from rat liver. At concentrations of 1-2 mg/ml, histones inhibited DNA synthesis. Bovine serum albumin had little effect on DNA synthesis. Polylysine caused an 80-90% inhibition at a concentration of 1 mg/ml, but stimulatory effects were detected under certain conditions at 10 microgram/ml. The results suggest critical dependence on the ratio of cell and exogenous protein concentration in the action of proteins on DNA synthesis.
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PMID:Actions of exogenous histones and other proteins on [3H]-thymidine incorporation into DNA of Novikoff hepatoma cells. 19 83

Euchromatic and heterochromatic fractions obtained by autodigestion of mouse TLT (taper liver tumour) hepatoma chromatin (Paul, I. J & Duerksen, J. D. (1976) Arch. Biochem. Biophys. 174, 491-505) were analyzed for relative protein content and histone content. With one exception, all fractions had the same DNA to protein ratio. Similarly, the total histone to DNA ratio was also constant in all fractions. In addition, the relative contents of the major histones, H1, (H2A + H2B + H3), and H4, were also constant in all fractions.
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PMID:Analyses of relative protein content and distribution of histones in euchromatic and heterochromatic fractions. 20 Mar 14


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