Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ultrastructural study of liver tissues from 38 patients with type B viral hepatitis consistently showed the presence of hepatitis B core antigen of 21-25 nm size in the liver cell nuclei and to a lesser extent in the cytoplasm. This finding and the demonstration of the tubular form of hepatitis B surface antigen in the proliferative degranulated endoplasmic reticulum constituted the etiologic criterion for the diagnosis of the disease. The double-shelled Dane-like particles were frequently found in association with the tubular form of the surface antigen. The core particles were found in the protoplasmic processes of hepatocytes and this correlated with the immunofluorescent microscopic findings that the antigen may be shed into circulation with the protoplasm. The core antigen was found to resist digestion by various enzymes such as protease, DNase, RNase, phospholipase C, lipase, lysozyme, diastase, neuraminidase and hyaluronidase, all of which did not destroy the immunoreactivity as demonstrated by immunoelectron and immunofluorescent microscopy. Similarly, sodium dodecyl sulfate, Tween 80 and mercaptoethanol also had no effect. The formalin-fixed paraffin-embedded liver tissue sections could be treated with protease to facilitate the immunofluorescent staining for the core antigen in tissue.
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PMID:Structural and immunoreactive characteristics of hepatitis B core antigen. 5 6

The expression of multidrug resistance (mdr) genes was investigated in the livers of transgenic mice that express the human hepatitis B virus large envelope polypeptide under the transcriptional control of a liver-specific promoter. These mice develop a storage disease due to the accumulation of a nonsecretable form of hepatitis B surface antigen in the hepatocyte. Liver cell injury is followed by a hepatocellular proliferative response, dysplasia, microscopic nodular hyperplasia, and finally hepatocellular carcinoma. The expression of mdr1, mdr2, and mdr3 genes was analyzed in livers at different stages of the disease by RNase protection assay, Western blot, and immunohistochemistry. RNase protection assay revealed that mdr3 mRNA expression was moderately increased in tissue with microscopic nodular hyperplasia and significantly overexpressed in hepatocellular carcinoma but undetectable in earlier stages of the disease. Western blot using isoform-specific anti-mdr3 antibody demonstrated that the expression of mdr3 protein reflected the steady-state level of mdr3 mRNA. Immunohistochemical analyses using anti-mdr3 isoform-specific antibody and monoclonal antibody C219, which recognizes all the three mdr isoforms, demonstrated selective overexpression in preneoplastic foci during the stage of microscopic nodular hyperplasia as well as in neoplastic hepatocytes in hepatocellular carcinoma. No consistent activation of mdr1 and mdr2 (but occasional coactivation with mdr1) genes during hepatocarcinogenesis was observed. Our results suggest that the hepatocellular mdr3-specific activation mechanism is associated with the late events of hepatocarcinogenesis in this model. The predictable kinetics of mdr gene expression in this transgenic tumor model suggest that it is suitable for future studies of the mechanism of mdr gene activation and the possible pharmacological consequences for mdr3 gene expression of hepatocellular carcinoma.
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PMID:Activation of multidrug resistance (P-glycoprotein) mdr3/mdr1a gene during the development of hepatocellular carcinoma in hepatitis B virus transgenic mice. 135 18

Transcription of the predominant surface antigen genes in Trypanosoma brucei is unusual in its resistance to the RNA polymerase inhibitor alpha-amanitin, a property typical for rDNA transcription in eukaryotes. Transcription of most other protein-coding genes in trypanosomes is sensitive to alpha-amanitin. To investigate whether RNA polymerase I, the polymerase that transcribes rRNA genes, can give rise to functional mRNAs in trypanosomes, we have fused the putative promoter of the T.brucei rRNA genes to the chloramphenicol acetyl transferase (CAT) gene and determined CAT activity after transient expression of chimeric constructs in procyclic trypanosomes. We show here that the rRNA promoter yields the same high CAT activity as the promoters for the two predominant surface antigen genes of trypanosomes, the Variant-specific Surface Glycoprotein (VSG) gene of bloodstream trypanosomes and the procyclin gene of insect-form trypanosomes, both of which are also transcribed by an alpha-amanitin-insensitive RNA polymerase. RNA polymerase I of trypanosomes seems therefore able to synthesize pre-mRNAs that are effectively processed into translatable mRNAs. Dissection of the promoter segments showed the minimal elements for a VSG gene expression site promoter to be confined to a segment of -60 to +77 bp, overlapping the most 5' putative transcription start sites as determined in vivo by RNase protection experiments. For the ribosomal promoter region a segment of -258 to +200 bp relative to the putative transcription start site was sufficient for maximal CAT activity. There is a precise requirement for specific nucleotides at the rRNA transcription start site. We detect no homology between the sequences required for promoter function of the three alpha-amanitin-resistant transcription units, rRNA, VSG and procyclin (parp) genes. This suggests that the sequence-specific recognition of these promoters either occurs by common factors detecting sequence homologies that escape us, or by separate factors that bind to different DNA sequences but interact with a common alpha-amanitin-resistant RNA polymerase.
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PMID:Alpha-amanitin-resistant transcription units in trypanosomes: a comparison of promoter sequences for a VSG gene expression site and for the ribosomal RNA genes. 192 1

1. Rabbit anti-(rat foetal liver) serum, absorbed with adult rat liver cells, decreased the electrophoretic mobility of foetal liver cells by 51% and rat hepatoma cells by 45%, indicating the presence of a foetal-type antigen on the hepatoma cell membrane. 2. The chemical nature of the surface antigen was investigated. Incubation with neuraminidase had no effect on adult liver cells but decreased the electrophoretic mobility of foetal liver cells by 51% and of hepatoma cells by 34%; the effect of antiserum was decreased to one-fifth. 3. Sialic acid, or the supernatant from neuraminidase-treated cells, partially blocked the decrease in electrophoretic mobility induced by antiserum. 4. The pH-electrophoretic mobility curves of hepatoma cells treated with antisera were consistent with a sialic acidcontaining antigen on the surface of the tumour cells. 5. Treatment with ribonuclease did not decrease the electrophoretic mobility of adult-liver cells, but decreased that of the foetal liver cells by 17% and hepatoma cells by 29%. 6. In parallel studies made with mouse BP8 ascites-tumour cells ribonuclease decreased the electrophoretic mobility by 39%, that of normal mouse lymph-node cells by 4.8% and allergized mouse lymph-node cells by 13.3%. 7. Trypsin treatment also decreased the electrophoretic mobility of hepatoma cells by 22%.
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PMID:A study of the cell surface of tumour, foetal and lymph-node cells by cell electrophoresis after antibody and enzymic treatment. 434 55

We identified, by anticomplement immunofluorescence, a nuclear antigen (hepatitis B virus-associated nuclear antigen [HBNA]) in two human hepatoma cell lines containing integrated hepatitis B virus DNA but not in three hepatoma cell lines lacking it. The antigen resembled neoantigens associated with the oncogenesis of certain papovaviruses, adenoviruses, and herpesviruses. Antibody to the antigen (anti-HBNA) was found in 7.3% of hepatitis B surface antigen-positive sera from patients with hepatocellular carcinoma but not in surface antigen-negative sera. The staining of HBNA was characterized by two patterns, reticular nuclear fluorescence and nucleolar fluorescence. The expression of HBNA did not parallel the production of extracellular hepatitis B surface antigen. Treatment of cells with proteinase K, RNase, DNase, or cycloheximide significantly diminished the staining of HBNA.
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PMID:Nuclear antigen detected in hepatoma cell lines containing integrated hepatitis B virus DNA. 630 93

Delta agent (delta) was serially passaged to a second and third hepatitis B surface antigen (HBsAg) carrier chimpanzee, using as inoculum the peak delta antigen (delta Ag) serum of an animal previously infected with human serum. The characteristics of serially transmitted delta Ag were similar to those described in first-passage animals. It was consistently detected before the development of anti-delta, in association with a 35- to 37-nm subpopulation of HBsAg particles and a unique low-molecular-weight (5.5 X 10(5)) RNA. RNase susceptibility of the delta-associated RNA and release of delta Ag activity upon treatment of delta-associated particles with detergent revealed that this particle is organized into a virion-like form with the RNA and delta Ag as internal components within a coat of HBsAg. Surface determinants of the delta-associated particle other than HBsAg were not detected by radioimmunoprecipitation experiments, using sera of humans and chimpanzees convalescent from delta hepatitis. The HBsAg-associated particle is the "candidate agent" of delta hepatitis.
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PMID:Delta hepatitis agent: structural and antigenic properties of the delta-associated particle. 669 98

The 96-kDa surface antigen of Entamoeba histolytica was demonstrated through extensive immunologic evaluation with monoclonal and monospecific antibodies to be identical to or an isoform of the amebic alcohol/aldehyde dehydrogenase (EhADH2). EhADH2 was secreted, excreted, or shed into the culture medium in quantities commensurate with amebic growth when studied in a novel culture system. Of importance, using RNase protection assays, specific mRNA coding for the EhADH2 gene product(s) was up-regulated by treatment of viable trophozoites with the enzyme substrate ethanol. These data provide insight into the biology of this enzyme and its regulation by appropriate stressors.
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PMID:Surface localization, regulation, and biologic properties of the 96-kDa alcohol/aldehyde dehydrogenase (EhADH2) of pathogenic Entamoeba histolytica. 853 63

We have shown that antisense oligonucleotides can be targeted to hepatitis B virus (HBV)-infected cells, resulting in specific inhibition of viral protein synthesis and replication in vitro. The targeting system was based on the internalization of DNA complexes by highly selective receptors for galactose-terminal glycoproteins, asialoglycoproteins, on the surface of hepatocytes. Our objective in this study was to determine whether antisense DNA could be targeted to hepatocytes to prevent subsequent infection by HBV. A 21-mer phosphorothioate-linked oligo DNA complementary to the HBV polyadenylation signal and 5'-upstream sequences was complexed to a targetable DNA carrier consisting of asialoglycoprotein coupled to polylysine. Pretreatment of Huh7, asialoglycoprotein receptor (+) cells, with antisense complexes before lipofection with an HBV-plasmid at a level of 6.5 x 10(6) copies of plasmid per cell inhibited the amount of newly synthesized, core-associated viral DNA in Huh7 cells to undetectable levels, less than 0.1 pg, as assessed by quantitative polymerase chain reaction (PCR). Hepatitis B viral RNA transcripts were decreased by 60% compared with controls as detected by RNase protection assays, and HBV surface antigen (HBsAg) accumulation was inhibited by 97%. The inhibition lasted for 6 days and was dose dependent. Controls consisting of antisense alone and a random oligo complex showed no significant effect on any of the parameters under identical conditions. We conclude that preexposure of cells to targeted complexed antisense DNA can substantially block viral gene expression and viral replication after transfection of HBV DNA.
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PMID:Inhibition of hepatitis B virus replication by targeted pretreatment of complexed antisense DNA in vitro. 867 42

CD36 is an 88-kD integral membrane protein expressed on platelets, monocytes, macrophages, certain microvascular endothelia, and retinal pigment epithelium. It functions as an adhesive receptor for thrombospondin-1 (TSP-1), collagen, and malaria-infected erythrocytes and as a scavenger receptor for oxidized LDL and photoreceptor outer segments. The CD36-TSP-1 interaction plays a role in cell adhesion and the phagocytosis of apoptotic cells by macrophages. Because of the potential importance of the CD36-TSP-1 interaction in mediating atherogenic and inflammatory processes, we studied their expression in human peripheral blood monocytes exposed to soluble mediators known to regulate inflammation and atherogenesis. RNase protection assays showed 6- to 12-fold increases in CD36 mRNA in response to interleukin-4, monocyte colony-stimulating factor, and phorbol myristate acetate, while lipopolysaccharide and dexamethasone strongly downregulated CD36 mRNA. The downregulation of CD36 mRNA was associated with the disappearance of surface expression of CD36 antigen and loss of TSP-1 surface-binding capacity. Upregulation of CD36 mRNA was associated with a modest increase in surface antigen expression and a larger expansion of an intracellular pool of CD36. As with CD36, monocytes treated with monocyte colony-stimulating factor showed a rapid increase in TSP-1 mRNA expression. Moreover, while dexamethasone treatment decreased CD36 expression, it resulted in a rapid increase in TSP-1 mRNA, and while PMA increased CD36 mRNA, it rapidly decreased TSP-1 expression. Interferon gamma, which had no effect on CD36 mRNA, rapidly increased steady-state TSP-1 mRNA. Thus, expression of both CD36 and its ligand TSP-1 is regulated by soluble mediators, although certain mediators induce concordant changes and others discordant changes.
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PMID:Regulation of monocyte CD36 and thrombospondin-1 expression by soluble mediators. 869 41

Recent studies suggest that interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) may play a central role in host defense and pathogenesis during Pneumocystis carinii pneumonia. In order to investigate whether the major surface antigen (MSG) of human P. carinii is capable of eliciting the release of IL-8 and TNF-alpha, human monocytes were cultured in the presence of purified MSG. MSG-stimulated cells released significant amounts of IL-8 within 4 h, and at 20 h, cells stimulated with MSG released 45.5 +/- 9.3 ng of IL-8/ml versus 3.7 +/- 1.1 ng/ml for control cultures (P = 0.01). In a similar fashion, MSG elicited release of TNF-alpha. Initial increases were also seen at 4 h, and at 20 h, TNF-alpha levels reached 6.4 +/- 1.1 ng/ml, compared to 0.08 +/- 0.01 ng/ml for control cultures (P < 0.01). A concentration-dependent increase in IL-8 and TNF-alpha secretion was observed at 20 h with 0.2 to 5 microg of MSG/ml (P < 0.01). Secretion of IL-8 and TNF-alpha from MSG-stimulated monocytes at 20 h was inhibited by 60 and 86%, respectively, after coincubation with soluble yeast mannan (P = 0.01). With an RNase protection assay, increases in steady-state mRNA levels for IL-8 and TNF-alpha were detectable at 4 h. These data show that recognition of MSG by monocytes involves a mannose-mediated mechanism and results in the release of the proinflammatory cytokines IL-8 and TNF-alpha.
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PMID:The major surface glycoprotein of Pneumocystis carinii induces release and gene expression of interleukin-8 and tumor necrosis factor alpha in monocytes. 935 66


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