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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using morphological and cell biological techniques, we have shown that the RNA replicase of Semliki Forest and Sindbis virus (two closely related alphaviruses) is located in complex ribonucleoprotein structures associated with the cytoplasmic surface of modified secondary lysosomes and endosomes. These nucleoprotein complexes often form a bridge between the membrane of the endocytic vacuole and the rough endoplasmic reticulum where the synthesis of the structural proteins of these viruses occurs. The results suggest that these cytopathic vacuoles constitute sites not only for viral RNA synthesis, but also for translation of structural proteins, and for the assembly of nucleocapsids.
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PMID:Alphavirus RNA replicase is located on the cytoplasmic surface of endosomes and lysosomes. 290 46

Hepatitis C virus is a positive single-strand RNA virus distantly related to flaviviruses. Therefore RNA replicase, an RNA-dependent RNA polymerase, may be essential for the replication of hepatitis C virus, as well as other RNA viruses. In this study we synthesized the recombinant polypeptide (HCV-NS5 antigen) with a 576 bp cDNA encoding a part of the NS5 region of the HCV genome that has the Gly-Asp-Asp motif. The antibody against this polypeptide was obtained from rabbit serum. In Western-blot analysis with NS5 IgG HCV antibody, an 84-kD protein was clearly detected as a single band in the microsomal fraction but not in the nuclear and mitochondrial fractions or in the cytosol fraction. Immunohistochemically, HCV-NS5 antigen was clearly stained in the cytoplasm of hepatocytes but not in the nucleus or cell membrane. Moreover, as determined on immunoelectron microscopy, HCV-NS5 antigen was demonstrated with fine granular distribution along the endoplasmic reticulum but not in other organelles, including the nucleus and mitochondria. Immunoreaction in other cell types was negative. These results indicate that replication of HCV may occur only in hepatocytes and that HCV-NS5 may be produced in the endoplasmic reticulum of these cells. HCV-NS5 antigen was stained only in the livers of hepatitis C virus-positive patients but not in sections from patients with chronic type B hepatitis or alcoholic fibrosis. In chronic type C liver disease, the overall detection rate of HCV-NS5 antigen was 56% (33% in chronic persistent hepatitis, 52% in chronic active hepatitis and 86% in cirrhosis).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Detection of antigens related to hepatitis C virus RNA encoding the NS5 region in the livers of patients with chronic type C hepatitis. 750 61

The double-stranded RNA genome of giardiavirus (GLV) has only two large open reading frame (ORFs). The 100-kDa capsid polypeptide (p100) is encoded by ORF1, whereas the only other viral polypeptide, the 190-kDa GLV RNA-dependent RNA polymerase (p190), is synthesized as an ORF1-ORF2 fusion protein by a (-1) ribosomal frameshifting. Edman degradation revealed that p100 was N-terminally blocked except for 2 to 5% of it that showed free N terminus starting from amino acid residue 33 of ORF1. Studies using antiserum targeted against amino acid residues 6 to 27 indicated that this region (NT) is absent from viral p100 and p190, while pulse-labelling experiments showed that NT is present in nascent p100 synthesized in GLV-infected Giardia lamblia but removed subsequently. In contrast, this region was retained in the two viral proteins synthesized in vitro, and it was not removed upon prolonged incubation or inclusion of microsomal fraction in the in vitro translation reaction mixtures. These results suggest that endoplasmic reticulum is not involved in the protein processing and that the precursors of p100 and p190 are incapable of cleaving themselves or each other. This specific cleavage was reproduced when lysates from GLV-infected G. lamblia were added, but not those from uninfected cells. The cleavage activity was relatively insensitive to phenylmethylsulfonyl fluoride, but it was inhibitable by leupeptin or E-64, two known specific inhibitors of cysteine protease. The possible origin of this processing activity is discussed.
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PMID:Maturation of giardiavirus capsid protein involves posttranslational proteolytic processing by a cysteine protease. 770 5

Plasmacytomagenesis provides a murine model to decipher progressive genetic events culminating in a B-cell neoplasia. Activation of the c-myc protooncogene by chromosomal translocation is considered an initiating event. Intracisternal A-type particles (IAPs) are defective retroviral-like structures present in the endoplasmic reticulum of plasmacytomas (PCTs). IAP proviral insertions have been documented to engender negative or positive effects on the expression of nearby cellular genes. We have isolated a gene, PANG (plasmacytoma-associated neuronal glycoprotein), that is ectopically transcribed in a number of PCTs due to IAP long terminal repeat (LTR) activation. A full-length PANG cDNA was isolated from an MPC-11 plasma cell tumor cDNA library and encodes a polypeptide of about 113 kDa with six immunoglobulin C2-like and four type III fibronectin-like domains. PANG bears a striking resemblance to axonal glycoproteins TAG-1 and F11 known to function in neuronal outgrowth. An extensive survey revealed a predominant 3.6-kb PANG transcript in 60% (30 of 50) of PCTs as well as unique smaller and larger species. All other normal and transformed lymphoid and nonlymphoid cell lines and normal tissues were negative for PANG expression except for the brain, wherein unique 4.0- and 6.1-kb transcripts were detected. Reverse transcriptase PCR analysis revealed IAP LTR fusion to PANG mRNAs in five PCTs and in a neuroblastoma line. The 5' end of a mouse brain PANG cDNA was identical to the MPC-11 PANG transcript except for the precise replacement of its 5' LTR sequence.
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PMID:PANG, a gene encoding a neuronal glycoprotein, is ectopically activated by intracisternal A-type particle long terminal repeats in murine plasmacytomas. 810 13

Inositol 1,4,5-trisphosphate (IP3) functions as a second messenger for many neurotransmitters, hormones and growth factors. It causes the release of Ca2+ from intracellular stores by binding to specific receptors that are coupled to Ca2+ channels. Recent studies have shown that there is a family of IP3 receptors, and the complete sequences of two members of this family and partial sequences of two others have been reported. We have determined the complete sequence of a third IP3 receptor, designated IP3R-3, and characterized its pharmacological properties and sites of expression. Rat IP3R-3 is 2670 amino acids in size, has 62 and 64% identity with IP3R-1 and IP3R-2, and is predicted to have a similar structure including a region of eight potential membrane-spanning segments at its COOH terminus, which presumably functions as a Ca2+ channel. Expression of recombinant rat IP3R-3 in COS-7 cells showed that it bound IP3 as well as inositol 1,3,4,5-tetrakisphosphate and inositol hexakisphosphate. Immunohistocytochemical studies of cells expressing recombinant IP3R-3 indicated that it has a preferential cellular distribution in the endoplasmic reticulum. RNA and protein blotting studies indicate that IP3R-3 is expressed in a number of different cultured cell lines including insulin-secreting RINm5F cells. The IP3R-3 is also expressed in adult pancreatic islets, kidney, gastrointestinal tract, and brain. Reverse transcriptase-polymerase chain reaction amplification of IP3R-1, -2, and -3 mRNAs in adult rat pancreatic islets indicated that IP3R-3 was the predominant subtype expressed in this tissue and thus may be responsible for mediating the effects of IP3 on insulin secretion.
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PMID:Sequence and functional characterization of a third inositol trisphosphate receptor subtype, IP3R-3, expressed in pancreatic islets, kidney, gastrointestinal tract, and other tissues. 838 91

Lysosomal degradation of ganglioside GM2 by beta-hexosaminidase A (hex A) requires the presence of the GM2 activator protein (GM2AP) as an essential cofactor. A deficiency of the GM2 activator causes the AB variant of GM2 gangliosidosis, a recessively inherited disorder characterized by excessive neuronal accumulation of GM2 and related glycolipids. Two novel mutations in the GM2 activator gene (GM2A) have been identified by the reverse-transcriptase-PCR method--a three-base deletion, AAG262-264, resulting in a deletion of Lys88, and a single-base deletion, A410, that causes a frameshift. The latter results in substitution of 33 amino acids and the loss of another 24 amino acid residues. Both patients are homoallelic for their respective mutations inherited from their parents, who are heteroallelic at the GM2A locus. Although the cultured fibroblasts of both patients produce normal levels of activator mRNA, they lack a lysosomal form of GM2AP. Pulse/chase labeling of cultured fibroblasts of the patients, in presence and absence of brefeldin A, indicates a premature degradation of both--mutant and truncated--GM2APs in the endoplasmic reticulum or Golgi. These results were supported by in vitro translation experiments and expression of the mutated proteins. When the mutated GM2APs were expressed in Escherichia coli, both mature GM2AP forms turned proved to exhibit only residual activities in an in vitro assay.
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PMID:Molecular analysis of a GM2-activator deficiency in two patients with GM2-gangliosidosis AB variant. 890 Feb 33

Peripheral primitive neuroectodermal tumors (PNETs) consistently demonstrate a reciprocal translocation, t(11;22)(q24;q12). This translocation has not been found in PNETs of the central nervous system including the cerebellar medulloblastoma. We report an unusual cerebellar PNET in a 4-year-old boy in which tumor cells were surrounded by pools of Alcian blue-positive material. Tumor cells were immunoreactive for neuron-specific enolase and synaptophysin. Electron microscopy revealed well-developed rough endoplasmic reticulum, cell processes with intermediate filaments, microtubules, and dense core granules, and extracellular material reminiscent of mucopolysaccharide. Reverse transcriptase polymerase chain reaction (PCR) revealed an 11;22 translocation-specific PCR product. Clinically the tumor was a cerebellar PNET with leptomeningeal dissemination and there was no evidence to suggest that it was metastatic. Histopathology, however, was indicative of an unusual PNET that also manifested t(11;22) and was associated with an aggressive clinical course.
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PMID:An unusual cerebellar primitive neuroectodermal tumor with t(11;22) translocation: pathological and molecular analysis. 896 22

Hepatitis C virus NS5B protein is an RNA-dependent RNA polymerase. To investigate the properties and function of this protein, we have expressed the NS5B protein in insect and mammalian cells. NS5B was found to be present as fine speckles in the cytoplasm, particularly concentrated in the perinuclear region, suggesting its association with the nuclear membrane, the endoplasmic reticulum, or the Golgi complex. This conclusion was supported by the biochemical demonstration that NS5B was associated with the membranes in the cells. Furthermore, it was shown that NS5B protein is a phosphoprotein. These properties may be related to its function as an RNA polymerase.
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PMID:Hepatitis C virus NS5B protein is a membrane-associated phosphoprotein with a predominantly perinuclear localization. 901 43

The cellular and molecular mechanisms underlying the postsynaptic aggregation of ionotropic receptors in the central nervous system are not understood. The glycine receptor (GlyR) and its cytoplasmic domain-associated protein, gephyrin, are clustered at the postsynaptic membrane and constitute a good model for addressing these questions. The glycine receptor is inhibited by strychnine. The effects of chronic strychnine treatment on the expression and cellular distribution of gephyrin and glycine receptor were therefore tested using primary cultures of spinal cord neurons. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed that the glycine receptor alpha1, alpha2, beta subunits and gephyrin mRNAs were expressed at comparable levels in strychnine-treated and untreated cultures. The number of immunoreactive cells and the subcellular distribution of gephyrin and GlyR subunits was determined with standard and confocal immunofluorescence. The proportion of gephyrin and glycine receptor-immunoreactive (IR) cells was unaffected by strychnine treatment. Confocal microscopy revealed that the glycine receptor was mainly localized intracellularly near the nucleus. This cytoplasmic glycine receptor was not associated with the Golgi apparatus nor with the rough endoplasmic reticulum and therefore is not likely to correspond to neosynthesized proteins. The number of GlyR clusters on the somato-dendritic membrane was dramatically reduced on neurons displaying intracellular staining. In contrast, the subcellular distribution and the number of gephyrin clusters was not modified by the treatment. The fact that gephyrin postsynaptic localization was not modified by strychnine suggests that the aggregation of glycine receptor and gephyrin is governed by different mechanisms. The distribution of other cell surface molecules such as NCAM or GABAA receptor beta2/3 subunits was not modified by strychnine treatment. Chronic exposure of the cultures to tetrodotoxin did not affect gephyrin or glycine receptor cluster formation. Taken together, these results indicate that functional glycine receptor, but not electrical synaptic activity, is required for the formation of glycine receptor clusters.
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PMID:Strychnine-sensitive stabilization of postsynaptic glycine receptor clusters. 942 82

The brain is an immunoprivileged organ isolated from the peripheral immune system. However, it has been shown that resident cells, notably astrocytes and microglia, can express numerous innate immune molecules, providing the capacity to generate a local antipathogen system. Perforin is a cytolytic protein present in the granules of cytotoxic T lymphocytes and natural killer cells. Expression in cells other than those of the hemopoetic lineage has not been described. We report here that fetal astrocytes in culture (passages 2 to 15), astrocytoma, and adult astrocytes expressed perforin. Reverse transcriptase polymerase chain reaction followed by Southern blot was carried out using multiple specific primers and all cDNAs were cloned and sequenced. Human fetal astrocyte perforin cDNA sequence was approximately 100% identical to the reported perforin cDNA cloned from T cells. Western blot analysis using monoclonal and polyclonal antiperforin peptide antibodies revealed a protein of 65 kD in both human fetal astrocyte and rat natural killer cell lysates (n = 4). Immunostaining followed by FACS(R) and confocal and electron microscopy analysis revealed that perforin was expressed by 40-50% of glial fibrillary acidic protein positive cells present in the fetal brain culture (n = 11). Perforin was not localized to granules in astrocytes but was present throughout the cytoplasm, probably in association with the endoplasmic reticulum. Perforin was not detected in normal adult brain tissue but was present in and around areas of inflammation (white and grey matter) in multiple sclerosis and neurodegenerative brains. Perforin-positive cells were identified as reactive astrocytes. These findings demonstrate that perforin expression is not unique to lymphoid cells and suggest that perforin produced by a subpopulation of astrocytes plays a role in inflammation in the brain.
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PMID:Identification of an astrocyte cell population from human brain that expresses perforin, a cytotoxic protein implicated in immune defense. 946 95


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