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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Proteoglycans are mediators of cellular adhesion and regulate growth factor activities. Proteoglycans of B lymphocytes undergo structural changes during B cell ontogeny which may correspond to the specific requirements of the respective microenvironment of the maturing cell. We analyzed three human B cell lines representing pre-B cells (Nalm-6), activated B cells (Jok-1) and plasma cells (U266) for their cellular proteoglycans. Gel filtration of the 35S-labeled macromolecules of the three cell lines revealed an increase in size in the order Nalm-6 < Jok-1 < U266. In Jok-1 and U266 cells the major pool of proteoglycans consisted of proteochondroitin sulfates of 50 to 90 kDa. These proteolglycans carried a protein core of approx. 30 kDa to which 1 to 3 glycosaminoglycan chains in the range of 28 to 32 kDa were attached. In Nalm-6 cells only free chondroitin sulfate chains of 23 kDa, but no intact proteoglycans, were detected. Chondroitin sulfate chains were predominantly composed of chondroitin-4-sulfate, those of Nalm-6 and U266 cells additionally contained 10-20% of unsulfated disaccharides. In U266 cells 30% of glycosaminoglycans consisted of heparan sulfate either bound to pure proteoheparan sulfate or to chondroitin sulfate/heparan sulfate hybrid-proteoglycans. Earlier, syndecan-1 was described as a hybrid proteoglycan containing heparan sulfate/chondroitin sulfate chains which is transcribed by murine B cells at early and late maturation stages. In order to see whether syndecan is transcribed by the human B cell lines used here, we measured expression of syndecan mRNA by the reverse transcriptase polymerase chain reaction. Similar to murine lymphocytes, syndecan-specific mRNA was detected in Nalm-6 and U266 cells, equivalent to early and late B cells, but not in lymphoblastoid Jok-1 cells. However, Nalm-6 cells do not produce proteoheparan sulfate. In these cells, syndecan synthesis may be blocked at the translational level. Also, the proteoglycans of U266 are different from syndecan-1 in their composition of glycosaminoglycans and in size of protein cores. Together, these results indicate that the major pool of proteoglycans produced by human B cells consists of proteochondroitin sulfate and additionally in later stages of a smaller proportion of proteoheparan sulfate which is not identical to syndecan-1. During distinct phases of B cell differentiation, modulations in the glycosaminoglycan moiety concerning size and sulfation of glycosaminoglycan chains were also found.
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PMID:Modulated glycosylation of proteoglycans during differentiation of human B lymphocytes. 777 69

The alpha T3-1 cell line, an immortalized gonadotroph cell line, expresses high levels of the gonadotrophin-releasing hormone (GnRH) receptor. Sustained exposure of these cells to the GnRH receptor agonist des-Gly10-[D-Ala6]luteinizing hormone-releasing hormone ethylamide resulted in a substantial down-regulation of cellular levels of a combination of the alpha subunits of the phospholipase C-beta 1-linked G proteins Gq and G11, as assessed by immunoblotting with an antiserum able to identify these two proteins equally. This effect was dependent upon the concentration of agonist used (EC50 = 4 nM) and on the time of the treatment (t1/2 = 6 hr) when a maximally effective concentration of agonist (1 microM) was used. Comparison of agonist regulation of inositol phosphate generation and Gq alpha/G11 alpha down-regulation demonstrated that effects on inositol phosphate production were approximately 3-fold more potent. In contrast to Gq alpha/G11 alpha, membrane-associated levels of Gs alpha and G12 alpha, the G proteins that transduce stimulatory and inhibitory regulation, respectively, of adenylyl cyclase, were not altered by agonist treatment. Analysis of mRNA by reverse transcriptase/polymerase chain reaction indicated the coexpression by alpha T3-1 cells of mRNA corresponding to both Gq alpha and G11 alpha. Immunoblotting with antisera selective for either Gq alpha or G11 alpha confirmed their coexpression. Resolution of membranes from untreated and agonist-treated alpha T3-1 cells under sodium dodecyl sulfate-polyacrylamide gel electrophoresis conditions able to separate Gq alpha from G11 alpha indicated that G11 alpha was more prevalent than Gq alpha at steady state but that agonist treatment regulated cellular levels of both of these G proteins in a nonselective manner. Sustained activation of protein kinase C with phorbol myristate acetate was unable to mimic agonist regulation of cellular Gq alpha/G11 alpha levels, as was treatment of alpha T3-1 cells with the selective protein kinase C inhibitor chelerythrine. These data suggest that the GnRH receptor is able to interact functionally with both Gq alpha and G11 alpha in alpha T3-1 cells and that sustained exposure to a GnRH receptor agonist selectively regulates the cellular levels of the G proteins that interact with the receptor.
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PMID:The gonadotrophin-releasing hormone receptor of alpha T3-1 pituitary cells regulates cellular levels of both of the phosphoinositidase C-linked G proteins, Gq alpha and G11 alpha, equally. 805 44

The role of cell-surface proteoglycans in human immunodeficiency virus (HIV) infection of T-cell lines was investigated. HIV-1-susceptible lymphoblastic T-cell lines, MT-4 and H9, were analyzed for proteoglycan synthesis and found to make heparan sulfate (HS) and chondroitin sulfate proteoglycans. Enzymatic treatment of these cells with heparitinase, but not chondroitinase, significantly prevented HIV-1(IIIB) infection as measured by inhibition of cytopathicity, reverse transcriptase production, and syncytia formation. Sulfation of glycosaminoglycans HS chains was critical to viral entry as shown by inhibition of viral infection with sodium chlorate and its specific reversal with exogenous sulfate addition. Quantitation of direct virus binding to cells showed that treatment of cells with heparitinase inhibited HIV-1 binding to the T-cell surface. Exogenous HS added to cultures inhibited virus infection in a manner analogous to dextran sulfate, further supporting a functional role for HS in HIV-1 binding. These results provide evidence for participation of cell-surface HS proteoglycans in HIV-cell attachment and virus entry.
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PMID:Cell-surface heparan sulfate proteoglycan mediates HIV-1 infection of T-cell lines. 809 45

The expression and extracellular release of transferrin receptor (TR) was investigated by in vitro model system of erythroid differentiation. Human peripheral blood mononuclear cells were cultured with interleukin-3 (IL-3) for 7 days, and with erythropoietin (EPO) for an additional 8 days. After EPO stimulation, IL-3-stimulated blastic cells were serially differentiated into mature erythrocytes. [3H]-thymidine incorporation of cultured cells increased linearly from day 0 to 5, followed by a decrease. Flow cytometric analysis showed an increase of TR expression from day 0 to 5, followed by a slight decrease. By metabolic labeling with [35S]methionine and immunoprecipitation, the cell lysate exhibited a 95-kD band corresponding to the intact TR on sodium dodecyl sulfate-polyacrylamide gel electrophoresis/autoradiography at day 5, when polychromatic erythroblasts had their peak. The culture supernatant solubilized by tween-20 exhibited a 95-kD and an 85-kD band on days 5 and 8, which corresponded to the intact and the truncated forms of TR, respectively. The 95-kD band was more intense at day 5 than at day 8. The reverse transcriptase-polymerase chain reaction assay showed that the receptor-mRNA expression was parallel to receptor synthesis. Thus, the synthesis and expression of TR on erythrocytes is associated mainly with cell proliferation in the early phase, and with both cell proliferation and hemoglobin production in the middle to late phases of maturation. Concomitantly, the extracellular release of TR from erythrocytes occurs in the middle to late phases of maturation. These data suggest that polychromatic erythroblasts release soluble TR as both intact and truncated forms and may be an important source of serum TR implicated as an index for erythropoietic activity in the marrow.
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PMID:Expression and extracellular release of transferrin receptors during peripheral erythroid progenitor cell differentiation in liquid culture. 811 25

Infection with simian immunodeficiency virus induces cytopathic effects on CEM x174 cells in vitro. Syncytium formation of SIV-infected CEM x174 cells was significantly enhanced in the presence of morphine sulfate, with a concomitant increase in the activity of cellular reverse transcriptase and in the expression of SIV p27 core antigen. Parallel establishment of the viability of the morphine-treated cells indicates that the short-acting opioid protects against cell lysis induced by SIV so that replication and production of SIV particles continued and exceeded those without morphine treatment. This delayed cell lysis induced by morphine as seen in vitro correlated with an in vivo observation that peripheral blood mononuclear cells isolated from morphine-treated rhesus macaques displayed a less degree of programmed cell death by apoptosis during early stages of SIVmac infection. These studies suggest that the modification of the biological properties of HIV-infected cells by morphine sulfate may be one of the mechanisms by which opioids exacerbate the progression of HIV in drug abusers.
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PMID:Increased replication of simian immunodeficiency virus in CEM x174 cells by morphine sulfate. 821 45

To address the question whether fish brain can produce insulin, pink salmon (Oncorhynchus gorbusha) brains were extracted and processed according to the procedure developed for purification of pancreatic insulin (Rusakov and Bondareva, 1979). Biological and immunological activity of the resulting material was evaluated respectively by a cartilage sulfation assay and by radioimmunoassay homologous for salmon insulin. Preparations from salmon brain stimulated the [35S]sulfate uptake into salmon branchial cartilage with a potency comparable to pure mammalian or salmon insulins but lower than that of mammalian insulin-like growth factor (IGF-I). In contrast, only trace amounts of radioimmunoreactive insulin could be detected by homologous radioimmunoassay. To determine whether insulin mRNA was present in salmon brain, primers specific for salmon proinsulin and salmon prepro-IGF-I were designed to amplify corresponding cDNA regions by reverse transcriptase-PCR. Insulin mRNA was found only in the endocrine pancreas (Brockmann body) while IGF-I mRNA was detected in the brain, liver, and the Brockmann body. Our results suggest that in fish pancreatic-type insulin is most likely produced only in the endocrine pancreas and then transported to the brain through blood/cerebrospinal fluid system. However, it does not exclude a possibility that some yet unknown insulin-like substances may be expressed in the neural system of ectotherm vertebrates.
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PMID:Does salmon brain produce insulin? 840 93

The syndecans comprise a family of integral membrane proteoglycans that regulate cell behaviors by binding to extracellular matrix and binding growth factors. In mouse blood cells, syndecan expression is restricted to cells of the B-cell lineage where it is expressed by pre-B cells and plasma cells, but is absent from circulating B cells. In the present study, we examined the expression, structure, and function of syndecan on human myeloma cell lines and myeloma patient bone marrow cells. On myeloma cells, syndecan is a small (modal relative molecular mass [M(r)] = 120 Kd) heparan sulfate proteoglycan localized at the cell surface. Syndecan was detected by immunodot blotting on 7 of 10 human myeloma cell lines and by reverse transcriptase polymerase chain reaction on 10 of 14 patient samples. Cell binding assays show that myeloma cells expressing syndecan bind to type I collagen via heparan sulfate chains, while those cell lines not expressing syndecan do not bind to collagen. Furthermore, the cell lines expressing syndecan were negative for CD19 and CD45 staining, indicating that syndecan expression is restricted to tumors having a well-differentiated phenotype. We conclude that syndecan acts as a matrix receptor on human myeloma cells but is not expressed by all tumors, suggesting that syndecan may participate in regulating myeloma cell adhesion to the bone marrow stromal matrix.
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PMID:Expression of syndecan regulates human myeloma plasma cell adhesion to type I collagen. 842 68

The target protein (enzyme) with which antiviral agents interact determines their antiviral activity spectrum. Based on their activity spectrum, antiviral compounds could be divided into the following classes: (1) sulfated polysaccharides (i.e., dextran sulfate), which interact with the viral envelope glycoproteins and are inhibitory to a broad variety of enveloped viruses (i.e., retro-, herpes-, rhabdo-, and arenaviruses): (2) SAH hydrolase inhibitors (i.e., neplanocin A derivatives), which are particularly effective against poxvirus, (-)RNA viruses (paramyxovirus, rhabdovirus), and (+/-)RNA virus (reovirus); (3) OMP decarboxylase inhibitors (i.e., pyrazofurin) and CTP synthetase inhibitors (i.e., cyclopentenylcytosine), which are active against a broad range of DNA, (+)RNA, (-)RNA, and (+/-)RNA viruses; (4) IMP dehydrogenase inhibitors (i.e., ribavirin), which are also active against various (+)RNA and (-)RNA viruses and, in particular, ortho- and paramyxoviruses; (5) acyclic guanosine analogs (i.e., ganciclovir) and carbocyclic guanosine analogs (i.e., cyclobut-G), which are particularly active against herpesviruses (i.e., HSV-1, HSV-2, VZV, CMV); (6) thymidine analogs (i.e., BVDU, BVaraU), which are specifically active against HSV-1 and VZV because of their preferential phosphorylation by the virus-encoded thymidine kinase; (7) acyclic nucleoside phosphonates (i.e., HPMPA, HPMPC, PMEA, FPMPA), which, depending on the structure of the acyclic side chain, span an activity spectrum from DNA viruses (papova-, adeno-, herpes-, hepadna-, and poxvirus) to retroviruses (HIV); (8) dideoxynucleoside analogs (i.e., AZT, DDC), which act as chain terminators in the reverse transcriptase reaction and thus block the replication of retroviruses as well as hepadnaviruses; and (9) the TIBO, HEPT, and other TIBO-like compounds, which interact specifically with the reverse transcriptase of HIV-1 and thus block the replication of HIV-1, but not of HIV-2 or any other retrovirus.
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PMID:Antiviral agents: characteristic activity spectrum depending on the molecular target with which they interact. 843 May 18

Decorin is a chondroitin/dermatan sulfate proteoglycan expressed by most vascular and avascular connective tissues and, because of its ability to interact with collagen and growth factors, has been implicated in the control of matrix assembly and cellular growth. To understand the molecular mechanisms involved in regulating its tissue expression, we have isolated a number of genomic clones encoding the complete decorin gene. The human decorin gene spans over 38 kb of continuous DNA sequence and contains eight exons and very large introns, two of which are 5.4 and > 13.2 kb. We have discovered two alternatively spliced leader exons, exons Ia and Ib, in the 5' untranslated region. These exons were identified by cloning and sequencing cDNAs obtained by polymerase chain reaction amplification of a fibroblast cDNA library. Using Northern blotting or reverse transcriptase PCR, we detected the two leader exons in a variety of mRNAs isolated from human cell lines and tissues. Interestingly, sequences highly (74-87%) homologous to exons Ia and Ib are found in the 5' untranslated region of avian and bovine decorin, respectively. This high degree of conservation among species suggests regulatory functions for these leader exons. In the 3' untranslated region there are several polyadenylation sites, and at least two of these sites could give rise to the transcripts of approximately 1.6 and approximately 1.9 kb, typically detected in a variety of tissues and cells. Using a genomic clone as the labeled probe and in situ hybridization of human metaphase chromosomes, we have mapped the decorin gene to the discrete region of human chromosome 12q23. This study provides the molecular basis for discerning the transcriptional control of the decorin gene and offers the opportunity to investigate genetic disorders linked to this important human gene.
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PMID:The human decorin gene: intron-exon organization, discovery of two alternatively spliced exons in the 5' untranslated region, and mapping of the gene to chromosome 12q23. 843 26

Sequences which control basal human T-cell lymphotropic virus type I (HTLV-I) transcription probably play an important role in initiation and maintenance of virus replication. We have identified and analyzed a 45-nucleotide sequence (downstream regulatory element 1 [DRE 1]) at the boundary of the R/U5 region of the long terminal repeat which is required for HTLV-I basal transcription. The basal promoter strength of constructs that contained deletions in the R/U5 region of the HTLV-I long terminal repeat were analyzed by chloramphenicol acetyltransferase assays following transfection of Jurkat T cells. We consistently observed a 10-fold decrease in basal promoter activity when sequences between +202 to +246 were deleted. By reverse transcriptase polymerase chain reaction RNA analysis, we confirmed that the drop in chloramphenicol acetyltransferase activity was paralleled by a decrease in the level of steady-state RNA. DRE 1 did not affect the level of Tax1 transactivation. Using a gel shift assay, we have purified a highly enriched fraction that could specifically bind DRE 1. This DNA affinity column fraction contained four detectable proteins on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis: p37, p50, p60, and p100. The affinity column fraction stimulated HTLV-I transcription approximately 12-fold in vitro. No effect was observed with the human immunodeficiency virus or adenovirus major late promoters. Following renaturation of the proteins isolated from an SDS-containing gel, p37, but not the other protein fractions, was able to specifically bind to DRE 1.
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PMID:Sequences downstream of the RNA initiation site regulate human T-cell lymphotropic virus type I basal gene expression. 847 78


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