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:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hormones play a role in the regulation of gene expression by inducing changes in enzyme patterns in target cells mediated by the synthesis of specific RNA molecules. Erythropoiesis has been used as a system for studying the molecular mechanism of regulation of gene action by means of two hormones: erythropoietin and testosterone. Experiments designed to correlate the biochemical action of both hormones on rat marrow cells are herein reported. Both factors seems to act at different biochemical and citological levels. Erythropoietin triggers the erythropoietic process acting on the erythropoietin sensitive cells (ESC), in which the hormone induces the synthesis of a high molecular weight RNA, which is the precursor of a functional 9 S messenger RNA. Testosterone seems to act on polychromatophilic erythroblasts, in which the synthesis of ribosomal RNA or its precursor is stimulated. The steroid enhances the nuclear ribonuclease activity, which could represent a control mechanism for the processing (maturation) of high molecular weight RNAs. The incorporation of 3H-GTP and 3H-UTP into RNA by isolated rat bone marrow nuclei is stimulated by erythropoietin and testosterone. Using alpha-amanitine and different ionic strength conditions it was found that erythropoietin enhances preferentially RNA polymerase II activity while testosterone increases RNA polymerase I activity. It is postulated that erythropoietin and testosterone act synergically to create the biochemical machinery for hemoglobin synthesis, the macromolecule that characterizes the erythropoietic process.
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PMID:Hormonal control of gene expression: differential activation of rat bone marrow RNA polymerases by erythropoietin and testosterone. 9 87

Globin gene switching in sheep and goats has been used as a model system for examining gene expression in differentiating red blood cells. Sheep and goats switch from the synthesis of hemoglobin A to hemoglobin C in response to erythropoietin. The regulatory mechanism producing this switch in hemoglobin types could occur at the cellular, nuclear, or cytoplasmic level. Evidence is presented which suggests that regulation is occurring, in fact, at the nuclear level. Sheep and goat erythroid colonies have been grown in plasma clot culture in order to study the synthesis of individual globin chains. Erythropoietin is required for colony formation. The switch from hemoglobin A to hemoglobin C synthesis requires not only colony formation but also a higher concentration of erythropoietin than is required just for the production of colonies. A cell-free transcriptional system using bone marrow chromatin and mammalian DNA-dependent RNA polymerase has been developed in order to examine the nuclear control mechanisms in more detail.
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PMID:Activation and inactivation of genes determining hemoglobin types.20s. 116 4

A base substitution in the 5'-flanking region of a human fetal globin gene is associated with abnormal fetal hemoglobin production. It also reduces by 5- to 10-fold in vitro transcription of the gene by RNA polymerase III. We discuss potential links between polymerase III transcription and abnormal hemoglobin production.
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PMID:Point mutation associated with hereditary persistence of fetal hemoglobin decreases RNA polymerase III transcription upstream of the affected gamma-globin gene. 243 Dec 98

The antigen-specific activation of murine nonimmunized B lymphocytes subsequently used in hybridization experiments has been investigated by using phylogenetically conserved antigens or autologous immunogens. This in vitro immunization was supported by B cell growth and differentiation factors derived from phorbol myristate acetate-stimulated EL-4 thymoma cells and mixed lymphocyte cultures (MLC). A filter immuno-plaque assay was used to evaluate the effect of different activation procedures on the number of antigen-specific plaque-forming cells (PFC). We first determined the requirement for MLC-derived lymphokines in the in vitro immunization. An optimal number of antigen-specific PFC was obtained when using 33 to 50% of the supernatant from a 48-hr MLC to support the activation. B cell growth and differentiation factors derived from EL-4 cultures were then tested for their abilities to potentiate the number of PFC by using both unseparated spleen cells and highly purified Ig-positive B cells as target cells. The combination of lymphokines found in supernatants from 25% EL-4 thymoma culture and 33% MLC yielded the highest number of PFC when used to support an in vitro immunization. This optimal factor preparation was used to determine the kinetics (4 to 7 days) and the dose response (0.01 to 10 micrograms antigen/ml) of antigen-specific B cell activation before using the immunized splenocytes as parental cells in cell fusion experiments. Mouse albumin and hemoglobin, actin (25 micrograms/ml), RNA polymerase II (5 micrograms/ml), as well as syngeneic mouse serum were used to immunize BALB/c spleen cells in vitro. We obtained antigen-specific PFC by using all of the different immunogens, including syngeneic mouse serum, and the in vitro immunized cells were then used in hybridization experiments. The specific efficiencies of each fusion that made use of cells immunized with mouse albumin, hemoglobin, syngeneic mouse serum, actin, or RNA polymerase II were 12, 31, 33, 52, and 22%, respectively, which illustrated the apparent lack of immune tolerance found when the immunization was performed in culture.
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PMID:In vitro immunization. Effect of growth and differentiation factors on antigen-specific B cell activation and production of monoclonal antibodies to autologous antigens and weak immunogens. 348 21

Globin messenger RNA, isolated from human peripheral blood reticulocytes, was transcribed into complementary DNA by use of the RNA-dependent DNA polymerase of avian myeloblastosis virus. The complementary DNA was then transcribed into (32)P-labeled complementary RNA by E. coli RNA polymerase in the presence of alpha-(32)P-labeled ribonucleoside triphosphates. The fingerprint pattern obtained from ribonuclease T1 digests of human globin complementary RNA was specific and reproducible. Different patterns were obtained from digests of duck, mouse, and rabbit globin complementary RNA. The fingerprint patterns obtained from digests of purified natural human 10S globin messenger RNA, labeled in vitro with (125)I or with [gamma-(32)P]ATP and polynucleotide kinase, were similar to that of the complementary RNA but contained some additional oligonucleotides. Sufficient nucleotide sequence information has been obtained from about 50% of the intermediate sized oligonucleotides (8-14 base residues long), to make possible examination of correspondence between these nucleotide sequences and globin amino-acid sequences. Approximately 70% of these oligonucleotide sequences can be matched to unique amino-acid sequences in the alpha- or beta-globin chains. The other 30% do not match known amino-acid sequences and presumably correspond to untranslated portions of the mRNA; some of these sequences, however, can be matched to amino-acid sequence in the abnormally long segment of the alpha chain of hemoglobin Constant Spring, which is thought to result from a chain-termination mutation.
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PMID:Nucleotide sequences of human globin messenger RNA. 413 9

A cytoplasmic, microsomal bound RNA-dependent RNA polymerase has been purified 2500-fold from rabbit reticulocyte lysates. The synthesis of RNA with the purified enzyme is absolutely dependent on the addition of an RNA template. The best template is hemoglobin messenger RNA, while bacteriophage RNA and poly(A,G) are less active, and DNA is completely inactive as a template. With poly(A,G) as a template, only UTP and CTP are incorporated into polynucleotide chains, indicating that the RNA polymerase is an RNA replicase and not a terminal transferase. With messenger RNA as a template, all four ribonucleoside triphosphates are required for maximal activity. The RNA-dependent RNA polymerase reaction is extremely sensitive to low concentrations of heme, rifamycin AF/013, and ribonuclease and resistant to actinomycin D and DNase. The discovery of RNA-directed RNA synthesis in reticulocytes offers an additional site for control of gene expression in mammalian cells and provides a possible mechanism for amplification of the expression of specific genes.
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PMID:Reticulocyte RNA-dependent RNA polymerase. 451 33

Cells of the line 3BM-78 derived from murine bone marrow cells infected in vitro with polycythemic Friend leukemia virus (FLV-P) produce virus with spleen focus-forming activity (SFFV) and can be induced to synthesize hemoglobin. Fifteen clones, isolated from this line, have been analyzed in detail for the effect of different inducing agents (dimethyl-sulfoxide, DMSO; hexamethylene bisacetamide, HMBA; and sodium butyrate, SB) on the synthesis of hemoglobin and virus at the clonal level. All the clones proved to be inducible with one or more of the agents, but the degree of the response depended on the type and concentration of the agent used. In general, the effectiveness of the agent--within the usual range of concentration for induction--both for hemoglobin and for virus synthesis, was in the order HMBA greater than DMSO greater than SB. Reverse transcriptase activity was, however, more easily induced than hemoglobin synthesis in that stimulation was seen at lower concentrations of the same inducing agent. This clonal analysis confirmed that virus and hemoglobin production are regulated independently in these erythroleukemic cells chronically infected with FLV-P.
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PMID:Variations in the response of cloned murine friend erythroleukemia cells to different inducers. 616 76

Interleukin-6 (IL-6) induced increased, leukocyte and platelet counts on around day 20 when it was administered into [BALB/c-->C3H/He] bone marrow chimeras from day 1 to day 12. Increased leukocyte counts and hemoglobin (Hb) levels were also observed at around day 60 and from day 41 to 80, respectively. On the other hand, hematopoietic recovery in [C3H/He-->C3H/He] bone marrow chimeras injected with IL-6 was different from that in [BALB/c-->C3H/He] bone marrow chimeras, showing no delayed and long-lasting increase in Hb levels but showing an early and transient increase in Hb levels and platelet counts. Sera from [BALB/c-->C3H/He] bone marrow chimeras injected with IL-6 showed predominant productions of IL-3 and/or IL-4. Reverse transcriptase polymerase chain reaction (RT-PCR) showed that stem cell factor (SCF) mRNA expression was increased in bone marrow or spleen cells from [BALB/c-->C3H/He] bone marrow chimeras injected with IL-6 on day 36. Furthermore, we analyzed influence of IL-6 on graft-versus-host disease (GVHD) in [BALB/c-->C3H/He] bone marrow chimeras injected with IL-6. Decreased survival days and body weights were not observed when compared with the control. Histopathological changes of the liver due to GVHD were also not obvious. However, alloreactive mixed lymphocyte reactions (MLRs) were readily detected although cytotoxic T cells were not generated. Since H-2 typing showed that donor-type chimerism was predominantly observed, it was suggested that split tolerance might be induced by IL-6 administration. Increased IL-2 levels were not detected in sera from [BALB/c-->C3H/He] bone marrow chimeras injected with IL-6 whereas IL-4 was detected in the same sera, indicating that type 2 helper T (TH2) cells appeared to be predominantly generated. These results suggest that IL-3/IL-4 and SCF appeared to synergistically support delayed effects on hematopoiesis in [BALB/c-->C3H/He] bone marrow chimeras injected with IL-6 although early effects appeared to be mediated mainly by IL-6 directly or indirectly. Furthermore, IL-6 could induce split tolerance in [BALB/c-->C3H/He] bone marrow chimeras via a preferable activation of TH2 type cells without inducing severe GVHD.
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PMID:In vivo administration of interleukin-6 in murine allogeneic bone marrow chimeras: early and delayed enhancement of hematopoiesis accompanied with split tolerance but not with graft-versus-host disease. 798 20

Unencapsulated Haemophilus influenzae is the second most common etiologic agent of otitis media in children. H. influenzae requires heme for aerobic growth in vitro and is able to utilize hemoglobin and complexes of heme-hemopexin, heme-albumin, and hemoglobin-haptoglobin and ferritransferrin as sources of iron and heme in vitro. Several of the acquisition mechanisms have been characterized and been shown to be heme repressible in vitro. However, little is known about the expression of heme and/or iron acquisition mechanisms during infections in the middle ear. This study was performed to determine if the genes encoding heme and iron acquisition proteins are transcribed during in vivo growth and to compare these findings with those for samples grown in vitro. Reverse transcriptase PCR (RT-PCR) was used to analyze total RNA fractions derived from in vitro- and in vivo-grown H. influenzae. Genes encoding the transferrin-binding proteins TbpA and TbpB, the 100-kDa hemopexin-binding protein HxuA, and the hemoglobin-binding protein HgpA were transcribed during otitis media. Twelve middle ear fluid samples were analyzed by blind RT-PCR to determine the transcriptional status of these genes in H. influenzae during otitis media. Five isolates had transcripts corresponding to tbpA, tbpB, and hxuA. The presence of hgpA transcripts was variable, depending on the presence of hgpA in the genome of the H. influenzae isolate. Samples without H. influenzae gene transcripts contained other etiologic agents commonly causing otitis media. These data demonstrate that H. influenzae iron and/or heme acquisition genes are transcribed during otitis media and suggest that the microenvironment during acute otitis media starves H. influenzae of heme.
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PMID:Transcription of genes encoding iron and heme acquisition proteins of Haemophilus influenzae during acute otitis media. 935 52

Increased levels of hemoglobin A(2) (HbA(2)) are present in most beta-thalassemia carriers. The mechanism of this effect is not understood, although the increase may result from transcriptional and posttranscriptional changes. In the present study, we quantitate delta-globin mRNA levels in peripheral-blood-enriched reticulocytes and characterize the variation of delta-mRNA levels in 30 beta-thalassemia heterozygotes who individually carry one of the four common Chinese beta-thalassemia alleles [codons 41/42 (-TTCT); codon 17 (A-->T); IVS-II-654 (C-->T); -28 (A-->G)]. A sensitive and quantitative competitive reverse-transcriptase polymerase chain reaction method was developed and used to assess the absolute amounts of delta-mRNA transcripts in these peripheral erythroid cells. The results showed a large increase in delta-mRNA amounts in all the carriers examined (72.3 +/- 9.0 amol/microg RNA) as compared with those in 12 controls (1.2 +/- 0.2 amol/ microg RNA). There was a direct correlation between the delta-mRNA levels and types of beta-thalassemia alleles; generally, the delta-mRNA levels are higher in heterozygotes for beta(0)-thalassemia mutations than beta(+)-thalassemia mutations. The delta-mRNA levels correlated inversely with hemoglobin and red cell indices but directly with HbA(2) levels in heterozygotes of each of the group of beta-thalassemia mutations. These results suggest that a greater impairment in beta-globin gene expression results in increased transcription of delta-globin gene and in a higher level of HbA(2).
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PMID:The delta-globin RNA transcript level in beta-thalassemia carriers. 1047 80


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