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)

CD34 is a cell surface antigen of unknown function expressed in humans in hematopoietic stem cells, vascular endothelium, and blasts from 30% of patients with acute myeloid and lymphocytic leukemia. To begin to investigate the cis-acting elements required for this tissue-specific expression, the human CD34 locus was isolated and its genomic structure and transcriptional start site were characterized. The human CD34 gene spans 26 kb and has 8 exons, a structure quite similar to that of the murine gene. The start site of CD34 transcription was determined to be 258 bp upstream of the translational start site using RNase protection. These experiments also indicated that the 5' untranslated region has extensive secondary structure. In addition, fluorescence in situ hybridization was used to map the CD34 locus to band 1q32.
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PMID:Structure of the gene encoding CD34, a human hematopoietic stem cell antigen. 137 51

Glucocorticoid treatment induces programmed cell death (apoptosis) in susceptible T lymphocytes. We have previously isolated and characterized 13 genes induced by agents that cause apoptosis in the murine thymoma cell line, WEHI-7TG. One of these genes, now designated Tcl-30, encodes a 2.4-kb mRNA that is specifically expressed in thymus. Sequence analysis of a full-length cDNA for Tcl-30 reveals a potential open reading frame of 454 amino acids that shares sequence identity to a human placental-specific protein of unknown function, PP11. The putative protein encoded by Tcl-30 also contains a cysteine-rich somatomedin B-like domain found in vitronectin, PP11, and the plasma cell membrane glycoprotein, PC-1. Subpopulations of murine thymocytes sorted on the basis of their expression of the CD4, CD8, and surface heat-stable Ag (HSA) were analyzed by an RNase protection assay to determine the expression of Tcl-30 as a function of T cell development. Tcl-30 was expressed exclusively in the HSA+ T cell populations (CD4-CD8-HSA+; CD4+CD8-HSA+; CD4-CD8+HSA+; and CD4+CD8+HSA+) and not in the HSA- single positive T cell populations (CD4+CD8- or CD4-CD8+) of the thymus or spleen. Therefore, we conclude that Tcl-30 expression is lost during T cell maturation and is absent at the most mature stages of T cell development. The function of Tcl-30 is unknown; however, the CD4+CD8+ double-positive subpopulation expressing Tcl-30 represents thymocytes destined to undergo massive intrathymic cell death. The possibility that Tcl-30 expression may define a population of T lymphocytes that is sensitive to glucocorticoid-mediated apoptosis is discussed.
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PMID:Tcl-30, a new T cell-specific gene expressed in immature glucocorticoid-sensitive thymocytes. 150 80

Surfactant is a lipoprotein substance that is synthesized and secreted by alveolar type II epithelial cells and acts to reduce surface tension at the air-alveolar interface. SP-C is a 5,000-D molecular weight, hydrophobic, surfactant-associated protein. In the present study, we used a ribonuclease protection assay to show that SP-C mRNA is induced in rabbit fetal lung tissue early in development, increases in relative concentration as development proceeds, and is present in maximal concentration at term (31 days of gestation). We also used the technique of in situ hybridization to localize SP-C mRNA in fetal, neonatal, and adult rabbit lung tissue. SP-C mRNA was present in all of the epithelial cells of the prealveolar region of day 19 gestational age rabbit fetal lung tissue, i.e., about 7 days before the appearance of differentiated alveolar type II cells in the fetal lung tissue. By day 27 of gestation, SP-C mRNA was restricted to epithelial cells with the morphologic characteristics of alveolar type II cells. SP-C mRNA was not detected in bronchiolar epithelium at any stage of lung development. The intensity of SP-C mRNA hybridization in the prealveolar and alveolar type II epithelial cells increased as a function of gestational age and was maximal at term. The pattern of SP-C mRNA localization in neonatal and adult rabbit lung tissue was consistent with the restriction of SP-C gene expression to differentiated alveolar type II cells. Our data are suggestive that SP-C may serve some as yet unknown function early in lung development because it is present in fetal lung prealveolar epithelial cells much earlier in gestation than are differentiated, surfactant-producing alveolar type II cells.
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PMID:Localization of surfactant-associated protein C (SP-C) mRNA in fetal rabbit lung tissue by in situ hybridization. 154 Mar 86

The Mov-34 mutation is a recessive embryonic lethal mutation caused by experimental introduction of a recombinant Moloney murine leukemia provirus into the mouse germline. We have cloned a full-length cDNA from the Mov-34 gene, the transcription unit disrupted by the proviral integration. This cDNA is predicted to encode a novel 321-amino acid, 36-kDa protein of unknown function. Overlapping phage lambda clones containing the entire Mov-34 gene have been isolated. The Mov-34 gene spans just over 8 kb and contains seven exons. The 5' flanking region of the Mov-34 gene contains neither "TATA" nor "CAAT" box sequences, and 5' end mapping by primer extension and ribonuclease protection reveal multiple transcription initiation sites.
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PMID:The murine Mov-34 gene: full-length cDNA and genomic organization. 183 87

DNA-directed RNA polymerase is responsible for gene expression. Despite its importance, many details of its function and higher-order structure still remain unknown. We report here a local sequence similarity between the second largest subunit of RNA polymerase II and bacterial RNases Ba (barnase), Bi, and St. The most remarkable similarity is that the catalytic sites of the RNases are shared with the eukaryotic RNA polymerase II subunits of Drosophila melanogaster and Saccharomyces cerevisiae. Several amino acids conserved among the RNases and the RNase-like domains of the RNA polymerase subunits are located in the neighborhood of the catalytic sites of barnase, whose three-dimensional structure has been resolved. This observation suggests the functional importance of the RNase-like domain of the RNA polymerase subunits and indicates that the RNase-like domain may have RNase activity. The location of the RNase-like domain relative to the region necessary for RNA polymerization is similar to the relative proximity of 5'----3' or 3'----5' exonuclease and the region of polymerase activity of DNA polymerase I. The RNase-like domain might work in proofreading, as in RNA-directed RNA polymerase of influenza virus, or it may contribute to RNA binding through an unknown function.
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PMID:RNase-like domain in DNA-directed RNA polymerase II. 192 68

Fetal liver or bone marrow-derived T lymphocyte precursors undergo extensive, developmentally regulated proliferation in response to inductive signals from the thymic microenvironment. We have used neonatal mouse thymocytes size-separated by centrifugal elutriation to study the cell cycle stage-specific expression of several genes associated with cell proliferation. These include genes involved in the biosynthesis of deoxyribonucleotide precursors, such as dihydrofolate reductase (DHFR), thymidylate synthase (TS), and the M1 and M2 subunits of ribonucleotide reductase, as well as c-myc, a cellular oncogene of unknown function. Using nuclear run-on assays, we observed that the transcription rates for these genes, with the exception of TS, are essentially invariant not only throughout the cell cycle in proliferating cells, but also in noncycling (G0) cells. The TS gene showed a transient increase in transcription rate in cells which bordered between a proliferating and nonproliferating status. Studies of an elutriated T cell line, S49.1, yielded similar results, indicating that the process of immortalization has not affected the transcriptional regulation of these genes. Analysis of steady-state mRNA levels using an RNase protection assay demonstrated that the levels of DHFR and TS mRNA accumulate as thymocytes progress through the cell cycle. In contrast, only the M2 subunit of ribonucleotide reductase showed cyclic regulation. Finally, in contrast to cultured cell models, we observed an abrupt fivefold increase in the steady-state level of c-myc mRNA in the transition from G1 to S-phase. We conclude from these studies that the transcriptional regulation of specific genes necessary for cellular proliferation is a minor component of the developmental modulation of the thymocyte cell cycle.
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PMID:A cell cycle analysis of growth-related genes expressed during T lymphocyte maturation. 227 81

Vitellogenesis in the frog hepatocyte was investigated by applying the protein A-gold immunocytochemical and RNase-gold cytochemical techniques in conjunction with morphometric and biochemical analyses. The morphometric studies demonstrated that the surface density of rough endoplasmic reticulum (RER) and nucleolar size increased more than fourfold and 1.25-fold, respectively, while the nuclear size and the mitochondrial compartment size remained constant following estrogen treatment. Concurrently, liver RNA concentration increased 2.5-fold while protein and DNA concentrations did not change. In addition, total plasma protein more than doubled, with vitellogenin accounting for 40% of the final volume. The secretory proteins vitellogenin and protein-RcX (a nonvitellogenin, estrogen-induced plasma protein of unknown function, found in the plasma of Rana catesbeiana) were detected immunocytochemically in the RER, Golgi apparatus, and secretory granules in hepatocytes only of estrogen-treated frogs. Lysosomes also were labeled. These observations established that protein-RcX was synthesized and secreted by the hepatocyte in parallel with vitellogenin and that both of these export proteins were confined to the secretory pathway and lysosomes. Quantitation of labeling density indicated that the concentration of vitellogenin increased as it progressed along the secretory vector. Albumin was detected immunocytochemically also within these same hepatocyte entities from both untreated and treated animals. In the untreated animals, albumin concentration also increased progressively along the secretory vector. A marked alteration of albumin processing was observed following estrogen treatment. While albumin concentration in the RER was unchanged, its concentrations within the Golgi apparatus and secretory granules were lower than those observed in the RER or in counterpart compartments under control conditions. RNase-gold cytochemistry for total RNA demonstrated a 1.5-fold increase in labeling density over the nucleolus but no change in RER labeling following estrogen treatment. These labeling data, in combination with the morphometric data, suggest an increase of approximately 80% in the total amount of RNA in the nucleolus and 430% in the RER in response to estrogen. This review thus illustrates the significant contributions which can be made by gold-probe techniques, alone or in combination with morphometric and biochemical techniques, to investigations of the intracellular processing of secretory proteins.
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PMID:Use of the protein A-gold immunocytochemical and enzyme-gold cytochemical techniques in studies of vitellogenesis. 278 86

Eukaryotic ribonucleases H of known sequence are composed of an RNase H domain similar in size and sequence to that of Escherichia coli RNase HI and additional domains of unknown function. The RNase H1 of Saccharomyces cerevisiae has such an RNase H domain at its C-terminus. Here we show that the N-terminal non-RNase H portion of the yeast RNase H1 binds tightly to double-stranded RNA (dsRNA) and RNA-DNA hybrids even in the absence of the RNase H domain. Two copies of a sequence with limited similarity to the dsRNA-binding motif are present in this N-terminus. When the first of these sequences is altered, the protein no longer binds tightly to dsRNA and exhibits an increase in RNase H activity. Unlike other dsRNA-binding proteins, increasing the Mg2+ concentration from 0.5 mM to 5 mM inhibits binding of RNase H1 to dsRNA; yet a protein missing the RNase H domain binds strongly to dsRNA even at the higher Mg2+ concentration. These results suggest that binding to dsRNA and RNase H activity are mutually exclusive, and the Mg2+ concentration is critical for switching between the activities. Changes in the Mg2+ concentration or proteolytic severing of the dsRNA-binding domain could alter the activity or location of the RNase H and may govern access of the enzyme to the substrate. Sequences similar to the dsRNA-binding motif are present in other eukaryotic RNases H and the transactivating protein of cauliflower mosaic virus, suggesting that these proteins may also bind to dsRNA.
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PMID:The non-RNase H domain of Saccharomyces cerevisiae RNase H1 binds double-stranded RNA: magnesium modulates the switch between double-stranded RNA binding and RNase H activity. 748 97

The isozymes of the 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) gene family are responsible for the formation of the 17 beta-hydroxysteroids delta 5-androstene-3 beta,17 beta-diol, testosterone, 17 beta-estradiol, and dihydrotestosterone from their corresponding 17-ketosteroid precursors, thus playing a pivotal role in the formation of active sex steroids in both steroidogenic and peripheral target tissues. To clone the type II 17 beta-HSD gene, the full-length cDNA type II 17 beta-HSD was used as probe to screen a human leukocyte genomic DNA library. The type II 17 beta-HSD gene contains seven exons and spans > 40 kbp. The type II 17 beta-HSD gene encodes two alternatively spliced mRNAs that give rise to the previously identified type IIA 17 beta-HSD protein of 387 amino acids, as well as to a related 291-amino-acid type IIB 17 beta-HSD protein of unknown function. RNA blot analysis revealed the presence of a major 1.45-kb transcript that is abundant in placenta and endometrium. The mRNA cap site has been localized in a region between 179 and 167 nucleotides upstream of the ATG start codon by RNase protection and S1 nuclease mapping analyses. Cloning of the 17 beta-HSD type II gene provides us with the tools to study its transcriptional expression.
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PMID:The human type II 17 beta-hydroxysteroid dehydrogenase gene encodes two alternatively spliced mRNA species. 754 91

The toxin coregulated pilus (TCP) is required for Vibrio cholerae to colonize the human intestine. The expression of the pilin gene, tcpA, is dependent upon ToxR and upon ToxT. The toxT gene was recently mapped within the TCP biogenesis gene cluster and shown to be capable of activating a tcpA::TnphoA fusion when cloned in Escherichia coli. In this study, we determined that ToxR/ToxT activation occurs at the level of tcpA transcription. ToxT expressed in E. coli could activate a tcp operon fusion, while ToxR, ToxR with ToxS, or a ToxR-PhoA fusion failed to activate the tcp operon fusion and we could not demonstrate binding of a ToxR extract to the tcpA promoter region in DNA mobility-shift assays. The start site for the regulated promoter was shown by primer extension to lie 75 bp upstream of the first codon of tcpA. An 800-base tcpA message was identified, by Northern analysis, that correlates by size to the distance between the transcriptional start and a hairpin-loop sequence between tcpA and tcpB. The more-sensitive assay of RNase protection analysis demonstrated that a regulated transcript probably extends through the rest of the downstream tcp genes, including toxT and the adjacent accessory colonization factor (acf) genes. An in-frame tcpA deletion, but not a polar tcpA::TnphoA fusion, could be complemented for pilus surface expression by providing tcpA in trans. This evidence suggests that the tcp genes, including toxT, are organized in an operon directly activated by ToxT in a ToxR-dependent manner. Most of the toxT expression under induced conditions requires transcription of the tcpA promoter. Further investigation of how tcp::TnphoA insertions that are polar on toxT expression retain regulation showed that a low basal level of toxT expression is present in toxR and tcp::TnphoA strains. Overall, these observations support the ToxR/ToxT cascade of regulation for tcp. Once induced, toxT expression becomes autoregulatory via the tcp promoter, linking tcp expression to that of additional colonization factors, exotoxin production, and genes of unknown function in cholera pathogenesis.
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PMID:Organization of tcp, acf, and toxT genes within a ToxT-dependent operon. 756 4


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