Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mitochondria isolated from Yoshida ascites hepatoma A.H. 130 cells are able to incorporate 3H-UTP into RNA. The reaction has been extensively characterized and appear to be supported by a typical DNA-dependent RNA polymerase, and no special differences with the system of normal rat liver mitochondria have been found.
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PMID:RNA synthesis by isolated Yoshida ascites hepatoma A.H. 130 cells mitochondria. 16 55

The synthesis of ribosomal precursor RNA in Novikoff hepatoma (N1S1) cells is very sensitive to cordycepin (3'-dA). The synthesis of hnRNA, however, is resistant to inhibition concentrations of 3'-dA that completely block the synthesis of 45S ribosomal RNA precursor. We have examined the RNA polymerases present in these cultured cells with regard to their sensitivity to cordycepin 5'-triphosphate (3'-dATP) in an effort to explain the differential inhibition of RNA synthesis observed in vivo. RNA polymerases I and II were characterized on the basis of their chromatographic behavior on DEAE-Sephadex, as well as the response of their enzymatic activities to ionic strength, the divalent metal ions Mn2+ and Mg2+, and the toxin alpha-amanitin. For both enzymes the inhibition of in vitro RNA synthesis by 3'-dATP was competitive for ATP. The km values for ATP and the K1 values for 3'-dATP for the two enzymes were quite similar. RNA polymerase II, the enzyme presumed responsible for hnRNA synthesis, was actually slightly more sensitive to 3'-dATP than RNA polymerase I, the enzyme presumed responsible for ribosomal precursor RNA synthesis. Similar data were obtained when the RNA polymerases were assayed in isolated nuclei. These results indicate that the differential inhibition of RNA synthesis caused by 3'-dA in vivo cannot be simply explained by differential sensitivity of RNA polymerases I and II to 3'-dATP.
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PMID:The sensitivity of RNA polymerases I and II from Novikoff hepatoma (N1S1) cells to 3'-deoxyadenosine 5'-triphosphate. 17 30

DNA-dependent RNA polymerases (EC 2.7.7.6) were extracted and partially purified form the nuclei of rat ascites hepatoma cells (AH-130) induced by 4-dimethylaminoazobenzene. The patterns of RNA synthesis and the properties of these enzymes were compared with enzymes from the nuclei of rat liver. The specific activity of RNA polymerase in the homogenate from the nuclei of AH-130 cells was the same as normal rat liver nuclei. RNA polymerase was solubilized from the homogenate at high ionic strength and separated into two forms by DEAE-Sephadex column chromatography. Enzymatic characterization showed that these enzymes corresponded to RNA polymerase I and II. RNA polymerase I more effectively transcribed native DNA than denatured DNA at low salt concentration, but at high salt concentration RNA polymerase I effectively transcribed denatured DNA. RNA polymerase II more effectively transcribed denatured DNA. In AH-130 cells the activity of RNA polymerase I was 4 to 5 times higher than RNA polymerase II, and in rat liver the activity of RNA polymerase I was 1.5 to 2 times higher than RNA polymerase II. The activity of RNA polymerase I in AH-130 cells may have increased by induction.
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PMID:A comparative study of DNA-dependent RNA polymerases from rat ascites hepatoma cell nuclei and from rat liver nuclei. 18 Jul 54

The nonhistone chromatin protein, C-14, was extracted from chromatin of Novikoff hepatoma ascites cells and isolated in high purity as shown by its migration as a single dense spot on two-dimensional polyacrylamide gels. Its mobility on sodium dodecyl sulfate gels is consistent with a molecular weight of approximately 70 000. The amino acid composition shows that protein C-14 has an acidic:basic amino acid ratio of 1.8. Its amino terminal amino acid is lysine. Protein C-14 stimulated the incorporation of [3H]UMP into RNA by approximately 30% when added to naked DNA and homologous RNA polymerase I. A 30% stimulation of [3H]UMP incorporation into RNA was also found when protein C-14 was added to an E. coli RNA polymerase system containing either E. coli or Novikoff hepatoma DNA.
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PMID:Isolation and characterization of nonhistone chromosomal protein C-14 which stimulates RNA synthesis. 19 58

An acidic nucleolar phosphoprotein with a subunit M(r) of 70,000 was purified as an apparent dimer of 139,000 from isolated nuclei of the slime mold Physarum polycephalum. The protein was purified without the aid of strong dissociating agents after its selective phosphorylation in isolated nuclei by a polyamine-mediated reaction. Its amino acid composition resembled that of a nucleolar phosphoprotein from Novikoff hepatoma ascites cells. The phosphoprotein stimulated rRNA synthesis 5-fold by RNA polymerase I within a nucleolar, ribosomal deoxyribonucleoprotein complex isolated from nucleoli of P. polycephalum. It was also identified as a component of the complex. It bound with high affinity and specificity to the palindromic ribosomal DNA of 38 x 10(6)M(r) from P. polycephalum, which contained two coding sequences for 5.8S, 19S, and 26S rRNA. It also bound to three fragments of ribosomal DNA of M(r) 21.2 x 10(6), 17.1 x 10(6), and 8.1 x 10(6), prepared by cleavage with restriction endonucleases HindIII, PstI, and BamHI, respectively. All of these fragments included the symmetry axis of the palindromic ribosomal DNA. The phosphoprotein that had been treated with alkaline phosphataseagarose to hydrolyze the phosphate groups did not stimulate transcription and did not bind to ribosomal DNA or to the restriction fragments indicated. We have thus isolated a specific phosphoprotein with the capacity to stimulate transcription of a specific set of genes in a eukaryote. These findings suggest that this phosphoprotein may specifically regulate functions of ribosomal DNA in a manner dependent on its degree of phosphorylation.
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PMID:Polyamine-mediated phosphorylation of a nucleolar protein from Physarum polycephalum that stimulates rRNA synthesis. 28 43

Patients with hepatocellular carcinoma (HCC), gastrointestinal, lung, and ovarian cancers were shown to have autoantibodies to nuclear and nucleolar antigens as detected by immunofluorescence on cell substrates. The frequency of antinuclear antibodies (ANAs) was significantly higher (P less than 0.001) in patients with HCC (57/184 = 31%) than in patients with chronic hepatitis or liver cirrhosis (25/187 = 13%). Although a range of fluorescence patterns was observed, a higher percentage of nucleolar fluorescence was detected in HCC, and three of these nucleolar antigens were identified. They were NOR-90, nucleolus organizer region doublet polypeptides of 93 and 89 kDa involved in RNA polymerase I transcription; fibrillarin, a 34 kDa protein of the nucleolar U3 ribonucleoprotein particle which is engaged in preribosomal RNA processing; and nucleophosmin/protein B23, a 37 kDa polypeptide which is associated with ribosome maturation and cellular proliferation. All these antigens are nucleolar components that are engaged in some aspect of ribosome biosynthesis. Since autoantibodies to these nucleolar antigens have also been found in systemic autoimmune diseases, they do not represent autoimmune reactions unique to cancer but might reflect reaction pathways related to immune responses that are antigen-driven. The ANA response in HCC appears to be dynamic reactions to this antigen-drive since some patients with chronic liver disease showed seroconversion to ANA positivity, marked increase in titer and/or change in antibody specificity preceding or coincident with clinical detection of HCC. These changes in ANA showed a close temporal relationship with transformation from long-established chronic liver disease to HCC.
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PMID:Nucleolar antigens and autoantibodies in hepatocellular carcinoma and other malignancies. 131 27

The protein components that direct and activate accurate transcription by rat RNA polymerase I were studied in extracts of Novikoff hepatoma ascites cells. A minimum of at least two components, besides RNA polymerase I, that are necessary for efficient utilization of templates were identified. The first factor, rat SL-1, is required for species-specific recognition of the rat RNA polymerase I promoter and may be sufficient to direct transcription by pure RNA polymerase I. Rat SL-1 directed the transcription of templates deleted to -31, the 5' boundary of the core promoter element (+1 being the transcription initiation site). The second factor, rUBF, increased the efficiency of template utilization. Transcription of deletion mutants indicated that the 5' boundary of the domain required for rUBF lay between -137 and -127. Experiments using block substitution mutants confirmed and extended these observations. Transcription experiments using those mutants demonstrated that two regions within the upstream promoter element were required for optimal levels of transcription in vitro. The first region was centered on nucleotides -129 and -124. The 5' boundary of the second domain mapped to between nucleotides -106 and -101. DNase footprint experiments using highly purified rUBF indicated that rUBF bound between -130 and -50. However, mutation of nucleotides -129 and -124 did not affect the rUBF footprint. These results indicate that basal levels of transcription by RNA polymerase I may require only SL-1 and the core promoter element. However, higher transcription levels are mediated by additional interactions of rUBF, and possibly SL-1, bound to distal promoter elements.
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PMID:Characterization of factors that direct transcription of rat ribosomal DNA. 234 70

Two cDNA clones isolated from a library prepared from dexamethasone-treated rat hepatoma cells have permitted us to detect the presence and the induction of heterogeneous, mainly short, RNA molecules in hepatoma cells and in rat liver, but not in several other rat tissues. The induction by dexamethasone is inhibited by 100 X progesterone. Pulse label experiments suggest that it occurs in part at least, at the level of transcription and may be mediated by RNA polymerase III. The induction of the RNAs is stimulated by cycloheximide, even in the absence of hormone, but not significantly by other stressful conditions. One line of hepatoma cells spontaneously lost its ability to induce these RNAs and synthesized them constitutively. These altered cells showed proper induction of another dexamethasone-mediated response, indicating that the glucocorticoid receptor was functionally normal in these cells. The two clones contain a type 2 Alu-like sequence. The short RNAs can be distinguished from 7SL RNA, which also contains Alu-sequences. We hypothesize that the synthesis of these RNAs may be regulated by an inhibitor of transcription which is inactivated by dexamethasone. Accordingly, cycloheximide relieves the inhibition by preventing synthesis of the inhibitor and the altered cell line has spontaneously lost the function of the inhibitor. The function of these RNAs for the cell is not known. We believe this to be the first report of hormone-regulated tissue specific synthesis of repeat-sequence transcripts.
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PMID:The induction of Alu-sequence transcripts by glucocorticoid in rat liver cells. 242

Antibody molecules directed against RNA polymerase I, the enzyme responsible for rRNA synthesis, were introduced into rat hepatoma cells by red cell-mediated microinjection. Access of the antibodies to the nucleolus, the site of rRNA synthesis, was facilitated by microinjecting mitotic cells. Using indirect immunofluorescence, anti-RNA polymerase I immunoglobulins, but not control immunoglobulins, were found localized in the nucleoli of microinjected cells. To assess whether intracellular antibodies could alter RNA synthesis, cultures were labeled with [3H] uridine at various times after microinjection. Reduction in RNA synthesis, relative to cells microinjected with non-immune immunoglobulins, was observed within three hours. These results demonstrate that antibodies introduced into the cytoplasm of mitotic cells via red cell-mediated microinjection have free access to nuclear components and that they remain functional within the nuclei of living cells.
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PMID:Reduction in RNA synthesis following red cell-mediated microinjection of antibodies to RNA polymerase I. 258 11

An in vitro transcription system was developed from H411EC3 (H4) hepatoma cells, which mimics the in vivo up-regulation by glucocorticoid hormones on ribosomal RNA (rRNA) synthesis. Ribosomal DNA (rDNA) transcription in extracts derived from H4 cells grown in the presence of 100 nM triamcinolone acetonide was 4- to 5-fold greater than that in extracts derived from cells grown in the absence of glucocorticoid. This effect was not a general stimulation by the steroid, as RNA polymerase II transcription of the metallothionein-1 gene which lacked a glucocorticoid responsive element was unaffected. The increased transcription in hormone-treated extracts was also independent of differential ribonuclease activities or inhibitors as ascertained by the inclusion of ribonuclease inhibitor and mixing experiments, respectively. Chromatography of H4 cell extracts on heparin-sepharose followed by transcription complementation analysis, showed that the hormone-induced stimulatory activity eluted with the fraction (TFIA) which contains RNA polymerase I (Pol I). Immunoblot analysis with specific anti-Pol I antibody showed similar subunit profiles in the absence and presence of the hormone. The presence of a Pol I enhancer element in addition to the rDNA promoter did not further modify the glucocorticoid-induced transcription. These results indicate that the glucocorticoid-mediated effects could be observed in cell extracts which accurately initiate transcription of cloned rat rDNA. Moreover, the alterations of rDNA transcription by the hormone is effected by a factor which elutes with fraction TFIA.
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PMID:Glucocorticoid-induced stimulation of ribosomal gene transcription in rat hepatoma cells is mediated by modification of RNA polymerase I or an associated factor. 260 60


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