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)

After interaction with its receptor, GM-CSF induces phosphorylation of the beta-chain in two distinct domains in macrophages. One induces activation of mitogen-activated protein kinases and the PI3K/Akt pathway, and the other induces JAK2-STAT5. In this study we describe how trichostatin A (TSA), which inhibits deacetylase activity, blocks JAK2-STAT5-dependent gene expression but not the expression of genes that depend on the signal transduction induced by the other domain of the receptor. TSA treatment inhibited the GM-CSF-dependent proliferation of macrophages by interfering with c-myc and cyclin D1 expression. However, M-CSF-dependent proliferation, which requires ERK1/2, was unaffected. Protection from apoptosis, which involves Akt phosphorylation and p21(waf-1) expression, was not modified by TSA. GM-CSF-dependent expression of MHC class II molecules was inhibited because CIITA was not induced. The generation of dendritic cells was also impaired by TSA treatment because of the inhibition of IRF4, IRF2, and RelB expression. TSA mediates its effects by preventing the recruitment of RNA polymerase II to the promoter of STAT5 target genes and by inhibiting their expression. However, this drug did not affect STAT5A or STAT5B phosphorylation or DNA binding. These results in GM-CSF-treated macrophages reveal a relationship between histone deacetylase complexes and STAT5 in the regulation of gene expression.
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PMID:Deacetylase activity is required for STAT5-dependent GM-CSF functional activity in macrophages and differentiation to dendritic cells. 1842 9

Whereas estrogens exert their effects by binding to nuclear estrogen receptors (ERs) and directly altering target gene transcription, they can also initiate extranuclear signaling through activation of kinase cascades. We have investigated the impact of estrogen-mediated extranuclear-initiated pathways on global gene expression by using estrogen-dendrimer conjugates (EDCs), which because of their charge and size remain outside the nucleus and can only initiate extranuclear signaling. Genome-wide cDNA microarray analysis of MCF-7 breast cancer cells identified a subset of 17beta-estradiol (E2)-regulated genes ( approximately 25%) as EDC responsive. The EDC and E2-elicited increases in gene expression were due to increases in gene transcription, as observed in nuclear run-on assays and RNA polymerase II recruitment and phosphorylation. Treatment with antiestrogen or ERalpha knockdown using small interfering RNA abolished EDC-mediated gene stimulation, whereas GPR30 knockdown or treatment with a GPR30-selective ligand was without effect, indicating ER as the mediator of these gene regulations. Inhibitors of MAPK kinase and c-Src suppressed both E2 and EDC stimulated gene expression. Of note, in chromatin immunoprecipitation assays, EDC was unable to recruit ERalpha to estrogen-responsive regions of regulated genes, whereas ERalpha recruitment by E2 was very effective. These findings suggest that other transcription factors or kinases that are downstream effectors of EDC-initiated extranuclear signaling cascades are recruited to regulatory regions of EDC-responsive genes in order to elicit gene stimulation. This study thus highlights the importance of inputs from both nuclear and extranuclear ER signaling pathways in regulating patterns of gene expression in breast cancer cells.
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PMID:Nuclear and extranuclear pathway inputs in the regulation of global gene expression by estrogen receptors. 1861 95

Natural killer (NK) cells are crucial components of the innate immune system, providing the first line of defense against infectious pathogens and tumors. Interleukin (IL)-12 is an interleukin produced primarily by antigen-presenting cells that play an essential role in the interaction between the innate and adaptive arms of immunity acting upon T and NK cells to generate cytotoxic lymphocytes. In the present study, we explored the effect of IL-12 upregulation on the NK receptor NKG2D and on the promotion of NK cell function. IL-12 enhanced the cytotoxicity of NK cells to different solid and hematological tumor cell lines and promoted interferon-gamma secretion by NK cells. The IL-12-induced cytolytic effect was dependent on the interaction of NKG2D with its ligand, MICA, because blockade of either protein attenuated the effect of IL-12 on NK cytolysis. Reverse transcriptase-polymerase chain reaction and fluorescence-activated cell sorting analyses indicated that IL-12 treatment increased NKG2D transcripts and surface expression in NK cells. Also, IL-12 augmented the expression of cytotoxic effector molecules, TRAIL and perforin, and the phosphorylation of STAT1, STAT4, and ERK1/2, which may also contribute to lysis by NK cells. These results are encouraging for the potential use of IL-12 as part of immunotherapy.
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PMID:Interleukin-12 improves cytotoxicity of natural killer cells via upregulated expression of NKG2D. 1861 7

The small hepatitis delta virus (HDV) antigen (SHDAg) plays an essential role in HDV RNA double-rolling-circle replication. Several posttranslational modifications (PTMs) of HDAgs, including phosphorylation, acetylation, and methylation, have been characterized. Among the PTMs, the serine 177 residue of SHDAg is a phosphorylation site, and its mutation preferentially abolishes HDV RNA replication from antigenomic RNA to genomic RNA. Using coimmunoprecipitation analysis, the cellular kinases extracellular signal-related kinases 1 and 2 (ERK1/2) are found to be associated with the Flag-tagged SHDAg mutant (Ser-177 replaced with Cys-177). In an in vitro kinase assay, serine 177 of SHDAg was phosphorylated directly by either Flag-ERK1 or Flag-ERK2. Activation of endogenous ERK1/2 by a constitutively active MEK1 (hemagglutinin-AcMEK1) increased phosphorylation of SHDAg at Ser-177; this phosphorylation was confirmed by immunoblotting using an antibody against phosphorylated S177 and mass spectrometric analysis. Interestingly, we found an increase in the HDV replication from antigenomic RNA to genomic RNA but not in that from genomic RNA to antigenomic RNA. The Ser-177 residue was critical for SHDAg interaction with RNA polymerase II (RNAPII), the enzyme proposed to regulate antigenomic RNA replication. These results demonstrate the role of ERK1/2-mediated Ser-177 phosphorylation in modulating HDV antigenomic RNA replication, possibly through RNAPII regulation. The results may shed light on the mechanisms of HDV RNA replication.
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PMID:ERK1/2-mediated phosphorylation of small hepatitis delta antigen at serine 177 enhances hepatitis delta virus antigenomic RNA replication. 1863 53

Microglial cells are the prime effectors in immune and inflammatory responses of the central nervous system (CNS). During pathological conditions, the activation of these cells helps restore CNS homeostasis. However, chronic microglial activation endangers neuronal survival through the release of various proinflammatory molecules and neurotoxins. Thus, negative regulators of microglial activation have been considered as potential therapeutic candidates to target neurodegeneration, such as that in Alzheimer's and Parkinson's diseases. Shikonin, a naphthoquinone pigment from the root of Lithospermum erythrorhizon, has long been used as an ointment for wound healing in traditional oriental medicine. Shikonin has been reported to have antibacterial, antitumor, and anti-inflammatory effects. The aim of this study was to examine whether shikonin represses microglial activation. In a study of shikonin and five of its derivatives, isobutyrylshikonin (IBS) and isovalerylshikonin (IVS) were the most effective at inhibiting LPS-induced nitric oxide (NO) release from microglial cells. Reverse transcriptase real-time PCR analysis revealed that pretreatment of rat brain microglia with IBS and IVS attenuated the LPS-induced expression of mRNAs encoding inducible NO synthase, tumor necrosis factor (TNF)-alpha, interleukin-1beta, and cyclooxygenase-2. In rat brain microglia, IBS and IVS reduced the LPS-stimulated production of TNF-alpha and prostaglandin E2. In addition, IBS and IVS significantly decreased LPS-induced IkappaB-alpha phosphorylation and NF-kappaB DNA binding activity, as well as the phosphorylation of the ERK1/2 and Akt signaling proteins. In organotypic hippocampal slice cultures, propidium iodide staining revealed prominent cell death in the hippocampal layer after 72h of LPS treatment. Both IBS and IVS clearly blocked the effect of LPS on hippocampal cell death and inhibited LPS-induced NO production in culture medium. These results suggest that IBS and IVS provide neuroprotection by reducing the release of various proinflammatory molecules from activated microglia.
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PMID:Shikonins attenuate microglial inflammatory responses by inhibition of ERK, Akt, and NF-kappaB: neuroprotective implications. 1865 51

It is well known that the mitogen-activated protein kinase (MAPK) signal transduction pathways is involved in the regulation of inducible nitric oxide synthase (iNOS) in many cellular systems. However, sufficient information describing the role of MAPKs on iNOS expression in rat Schwann cells (SCs) is lacking. Therefore the paper was sought to investigate the role of MAPK cascades in iNOS expression following treatment of lipopolysaccharide (LPS) in a rat Schwann cell line RSC 96. Reverse transcriptase-PCR analysis (RT-PCR) and immunocytochemical staining were performed to detect iNOS expression following LPS induction. Next RT-PCR and Western blot analysis were employed to study expression of iNOS after using inhibitors selective for ERK (PD98059), JNK/SAPK (SP600125) and p38 (SB202190). The production of nitric oxide (NO) was measured by nitrate reductase method. LPS could significantly induce the expression of iNOS located in the cytoplasm in RSC 96 with a concentration- and time-dependent manner. Administration of inhibitors individually and combinations of the three inhibitors at micromolar concentrations suppressed the expression of iNOS and the production of NO. Based on these observations, it is proposed that LPS may activate the rat Schwann cell line RSC 96 to express iNOS and release NO via the MAPK signal transduction pathways.
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PMID:Role of mitogen-activated protein kinase cascades in inducible nitric oxide synthase expression by lipopolysaccharide in a rat Schwann cell line. 1866 65

The transcription rate of immediate early genes (IEGs) is controlled directly by transcription elongation factors at the transcription elongation step. Negative elongation factor (NELF) and 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) sensitivity-inducing factor (DSIF) stall RNA polymerase II (pol II) soon after transcription initiation. Upon induction of IEG transcription, DSIF is converted into an accelerator for pol II elongation. To address whether and how NELF as well as DSIF controls overall IEG transcription, its expression was reduced using stable RNA interference in GH4C1 cells. NELF knock-down reduced thyrotropin-releasing hormone (TRH)-induced transcription of the IEGs c-fos, MKP-1, and junB. In contrast, epidermal growth factor (EGF)-induced transcription of these IEGs was unaltered or even slightly increased by NELF knock-down. Thus, stable knock-down of NELF affects IEG transcription stimulation-specifically. Conversely, DSIF knock-down reduced both TRH- and EGF-induced transcription of the three IEGs. Interestingly, TRH-induced activation of the MAP kinase pathway, a pathway essential for transcription of the three IEGs, was down-regulated by NELF knock-down. Thus, stable knock-down of NELF, by modulating intracellular signaling pathways, caused stimulation-specific loss of IEG transcription. These observations indicate that NELF controls overall IEG transcription via multiple mechanisms both directly and indirectly.
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PMID:Negative elongation factor NELF controls transcription of immediate early genes in a stimulus-specific manner. 1901 35

In mammals, the mechanisms regulating the number of active copies of the approximately 200 ribosomal RNA (rRNA) genes transcribed by RNA polymerase I are unclear. We demonstrate that depletion of the transcription factor upstream binding factor (UBF) leads to the stable and reversible methylation-independent silencing of rRNA genes by promoting histone H1-induced assembly of transcriptionally inactive chromatin. Chromatin remodeling is abrogated by the mutation of an extracellular signal-regulated kinase site within the high mobility group box 1 domain of UBF1, which is required for its ability to bend and loop DNA in vitro. Surprisingly, rRNA gene silencing does not reduce net rRNA synthesis as transcription from remaining active genes is increased. We also show that the active rRNA gene pool is not static but decreases during differentiation, correlating with diminished UBF expression. Thus, UBF1 levels regulate active rRNA gene chromatin during growth and differentiation.
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PMID:UBF levels determine the number of active ribosomal RNA genes in mammals. 1910 6

The RAS-mitogen-activated protein kinase signaling pathway is often deregulated in cancer cells. In metastatic HRAS-transformed mouse fibroblasts (Ciras-3), the RAS-MAPK pathway is constitutively activated. We show here that Ciras-3 cells exhibit a higher incidence of chromosomal instability than 10T1/2 cells, including higher levels of clonal and nonclonal chromosomal aberrations. Stimulation of serum starved 10T1/2 and Ciras-3 cells with phorbol esters (TPA) results in the phosphorylation of histone H3 at serine 10 and serine 28. Regardless of the increased genomic instability in Ciras-3 cells, TPA-induced H3 phosphorylated at serine 10 and H3 phosphorylated at serine 28 partitioned into distinct nuclear subdomains as they did in the parental cells. However, the timing of the response of the H3 phosphorylation event to TPA induction was delayed in Ciras-3 cells. Further Ciras-3 cells, which have a more open chromatin structure, had increased steady state levels of phosphorylated H3 and HMGN1 relative to parental 10T1/2 cells. TPA-induced H3 phosphorylated at serine 10 and 28 were colocalized with the transcriptionally initiated form of RNA polymerase II in 10T1/2 and Ciras-3 cells. Chromatin immunoprecipitation assays demonstrated that TPA-induced H3 phosphorylation at serine 28 was associated with the immediate early JUN promoter, providing direct evidence that this histone post-translational modification is associated with transcriptionally active genes. Together our results demonstrate the increased genomic instability and alterations in the epigenetic program in HRAS-transformed cells.
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PMID:Increased genomic instability and altered chromosomal protein phosphorylation timing in HRAS-transformed mouse fibroblasts. 1919 Dec 62

Reversible protein phosphorylation is a signaling mechanism involved in all cellular processes. To create a systems view of the signaling apparatus in budding yeast, we generated an epistatic miniarray profile (E-MAP) comprised of 100,000 pairwise, quantitative genetic interactions, including virtually all protein and small-molecule kinases and phosphatases as well as key cellular regulators. Quantitative genetic interaction mapping reveals factors working in compensatory pathways (negative genetic interactions) or those operating in linear pathways (positive genetic interactions). We found an enrichment of positive genetic interactions between kinases, phosphatases, and their substrates. In addition, we assembled a higher-order map from sets of three genes that display strong interactions with one another: triplets enriched for functional connectivity. The resulting network view provides insights into signaling pathway regulation and reveals a link between the cell-cycle kinase, Cak1, the Fus3 MAP kinase, and a pathway that regulates chromatin integrity during transcription by RNA polymerase II.
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PMID:Functional organization of the S. cerevisiae phosphorylation network. 1926 70


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