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)

Washed mature spermatozoa from bulls incorporate ribonucleoside triphosphates into RNA using an endogenous template. Maximum incorporation was observed at 31 degrees C in the presence of MgCl2, all four ribonucleoside triphosphates, beta-mercaptoethanol, and glycine sodium hydroxide buffer at pH 9.0. The amount of synthesis was linearly dependent upon the concentration of spermatozoa and continued for at least 4 h. Digestion studies revealed the RNA to be present in a protected (intracellular?) location in the spermatozoa. The RNA synthesis was inhibited by ethidium bromide, rifampicin, acriflavine, actinomycin D, and caffeine, but not by alpha-amanitine or rifamycin SV. Fractionation of the spermatozoa by sonication and separation of the heads and tails by centrifugation through a discontinuous gradient revealed that more than half of the total RNA polymerase activity was associated with the tail fraction.
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PMID:RNA polymerase activity in bovine spermatozoa. 2 Apr 46

Intermediate subviral particles (ISVP) derived from reovirus represent a simple model system for the switch-on of transcriptase function. In such particles the endogenous transcriptase is present in a switched-off form, one step removed from the switched-on state. Switch-on of transcriptase function is an active process in this system and can be triggered by K+ions. A variety of agents which affect gene expression in cells were tested for an effect on switch-on in ISVP. Marked effects on switch-on in ISVP were observed with a diverse group of test agents, including DMSO and other solvents, BUdR, TdR, caffeine, theophylline, and temperature. The correlation in response between ISVP and cells suggests that the ISVP system may be useful as a model for studying the biochemical mechanisms underlying the perturbative effects of such agents on gene expression in cells.
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PMID:Perturbation of the switch-on of transcriptase activity in intermediate subviral particles from reovirus. 617 50

Administration of caffeine or theophylline, 0.2 mg/ml (an average of 20 mg/kg/d) of drinking water, to male CD rats, 2 months of age, over a 15 week period resulted in the elevation of liver RNA polymerase I activity by 2-3 fold as assayed in isolated nuclei. This increase in activity was already apparent by the fourth week of exposure. The changes in RNA polymerase I activity were accompanied by moderate liver hypertrophy.
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PMID:Subchronic administration of caffeine and theophylline in drinking water: effects on rat liver RNA polymerase I activity. 731 87

In excitable cells, oscillations in intracellular free calcium concentrations ([Ca(2+)](i)) can arise from action-potential-driven Ca(2+) influx, and such signals can have either a localized or global form, depending on the coupling of voltage-gated Ca(2+) influx to intracellular Ca(2+) release pathway. Here we show that rat pituitary somatotrophs generate spontaneous [Ca(2+)](i) oscillations, which rise from fluctuations in the influx of external Ca(2+) and propagate within the cytoplasm and nucleus. The addition of caffeine and ryanodine, modulators of ryanodine-receptor channels, and the depletion of intracellular Ca(2+) stores by thapsigargin and ionomycin did not affect the global nature of spontaneous [Ca(2+)](i) signals. Bay K 8644, an L-type Ca(2+) channel agonist, initiated [Ca(2+)](i) signaling in quiescent cells, increased the amplitude of [Ca(2+)](i) spikes in spontaneously active cells, and stimulated growth hormone secretion in perifused pituitary cells. Nifedipine, a blocker of L-type Ca(2+) channels, decreased the amplitude of spikes and basal growth hormone secretion, whereas Ni(2+), a blocker of T-type Ca(2+) channels, abolished spontaneous [Ca(2+)](i) oscillations. Spiking was also abolished by the removal of extracellular Na(+) and by the addition of 10 mM Ca(2+), Mg(2+), or Sr(2+), the blockers of cyclic nucleotide-gated channels. Reverse transcriptase-polymerase chain reaction and Southern blot analyses indicated the expression of mRNAs for these channels in mixed pituitary cells and purified somatotrophs. Growth hormone-releasing hormone, an agonist that stimulated cAMP and cGMP productions in a dose-dependent manner, initiated spiking in quiescent cells and increased the frequency of spiking in spontaneously active cells. These results indicate that in somatotrophs a cyclic nucleotide-controlled plasma membrane Ca(2+) oscillator is capable of generating global Ca(2+) signals spontaneously and in response to agonist stimulation. The Ca(2+)-signaling activity of this oscillator is dependent on voltage-gated Ca(2+) influx but not on Ca(2+) release from intracellular stores.
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PMID:Characterization of a plasma membrane calcium oscillator in rat pituitary somatotrophs. 1058 49

A yeast strain harboring a temperature-sensitive allele of TFB3 (tfb3(ts)), the 38-kDa subunit of the RNA polymerase II transcription/nucleotide excision repair factor TFIIH, was found to be sensitive to ultraviolet (UV) radiation and defective for nucleotide excision repair in vitro. Interestingly, tfb3(ts) failed to grow on medium containing caffeine. A comprehensive pairwise two-hybrid analysis between yeast TFIIH subunits identified novel interactions between Rad3 and Tfb3, Tfb4 and Ssl1, as well as Ssl2 and Tfb2. These interactions have facilitated a more complete model of the structure of TFIIH and the nucleotide excision repairosome.
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PMID:Subunit interactions in yeast transcription/repair factor TFIIH. Requirement for Tfb3 subunit in nucleotide excision repair. 1068 87

1. The mobilization of Ca2+ by purinoceptor activation and the relative contributions of intra- and extracellular sources of Ca2+ were investigated using microfluorimetric measurements of fura-2 loaded in cultured neurones from rat intracardiac ganglia. 2. Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed expression of mRNA for the G protein-coupled P2Y2 and P2Y4 receptors. 3. Brief application of either 300 microM ATP or 300 microM UTP caused transient increases in [Ca2+]i of 277 +/- 22 nM and 267 +/- 39 nM, respectively. Removal of external Ca2+ did not significantly reduce these [Ca2+]i responses. 4. The order of purinoceptor agonist potency for [Ca2+]i increases was ATP = UTP > 2-MeSATP > ADP >> adenosine, consistent with the profile for P2Y2 purinoceptors. ATP- and UTP-induced rises in [Ca2+]i were completely and reversibly blocked by 10 microM PPADS (a P2 purinoceptor antagonist) and partially inhibited by 100 microM suramin (a relatively non-specific purinoceptor antagonist). 5. In the presence of the endoplasmic reticulum Ca2+-ATPase inhibitor cyclopiazonic acid (10 microM) in Ca2+-free media, the [Ca2+]i responses evoked by ATP were progressively decreased and abolished. 6. ATP- and UTP-induced [Ca2+]i rises were insensitive to pertussis toxin, caffeine (5 mM) and ryanodine (10 microM) but were significantly reduced by U-73122, a phospholipase C (PLC) inhibitor. 7. In fura-2-loaded cells, perforated patch whole-cell recordings show that ATP and UTP evoked slow outward currents at -60 mV, concomitant with the rise in [Ca2+]i, in approximately 30 % of rat intracardiac neurones. 8. In conclusion, these results suggest that in r intracardiac neurones, ATP binds to P2Y2 purinoceptors to transiently raise [Ca2+]i and activate an outward current. The signalling pathway appears to involve a PTX-insensitive G protein coupled to PLC generation of IP3 which triggers the release of Ca2+ from a ryanodine-insensitive Ca2+ store(s).
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PMID:P2Y purinoceptor activation mobilizes intracellular Ca2+ and induces a membrane current in rat intracardiac neurones. 1089 18

Human bronchial smooth muscle (HBSM) contraction is implicated in a variety of respiratory diseases, including asthma. Yet, the presence of an operative calcium-induced calcium release (CICR) mechanism, identified in various smooth muscles, has not been established in HBSM. We therefore studied Ca-releasing mechanisms in HBSM obtained at thoracotomy with special attention to ryanodine-sensitive receptor channels (RyRs). In freshly isolated bronchial myocytes, ryanodine (0.5 to 50 microM) and caffeine (1 to 25 mM) induced transient increases in the cytoplasmic calcium concentration ([Ca(2+)](i)). Higher ryanodine concentrations (> 100 microM) inhibited the caffeine-induced [Ca(2+)](i) response, which was also blocked in the presence of tetracaine (300 microM) or ruthenium red (200 microM), two potent CICR inhibitors. In HBSM strips, caffeine induced a transient contraction which, likewise, was inhibited by ryanodine and tetracaine. However, ryanodine (200 microM) modified neither the [Ca(2+)](i) response nor the contraction induced by K(+)-rich (110 mM) solution. Reverse transcriptase/polymerase chain reaction (RT-PCR) and RNase protection assay performed in HBSM have revealed the existence of mRNAs encoding only the type 3 RyR. We also characterized acetylcholine-induced [Ca(2+)](i) and contractile responses. None of these responses was altered by ryanodine or by tetracaine. These results demonstrate, for the first time, the existence of functional RyRs in HBSM cells which, owing to the type of isoform or the amount of protein expressed, are not involved, under physiologic conditions, in depolarization- or agonist-induced contraction.
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PMID:Human isolated bronchial smooth muscle contains functional ryanodine/caffeine-sensitive Ca-release channels. 1093 7

The effects of caffeine on both levcromakalim-induced macroscopic and unitary currents in pig proximal urethra were investigated by the use of patch-clamp techniques (conventional whole-cell configuration and cell-attached configuration). The effects of caffeine were also examined on currents in inside-out patches of COS7 cells expressing carboxy terminus truncated inwardly rectifying K(+) channel (Kir6.2) subunits (i.e. Kir6.2DeltaC36) which form ATP-sensitive K(+) channels (K(ATP) channels). In conventional whole-cell configuration, the levcromakalim (100 microM)-induced inward current (symmetrical 140 mM K(+) conditions) was inhibited by caffeine (> or =1 mM) at a holding potential of -50 mV. In contrast, ryanodine (10 microM) caused no significant inhibitory effect on the gradual decay of the levcromakalim-induced current at -50 mV. The amplitude of the 30 microM levcromakalim-induced current was enhanced by 3-isobutyl-1-methylxanthine (IBMX, 100 microM). In cell-attached configuration, the levcromakalim-induced K(+) channel openings were inhibited by subsequent application of 10 mM caffeine, decreasing the channel open probability at -50 mV. Reverse transcriptase-polymerase chain reaction (RT - PCR) analysis revealed the presence of Kir6.2 transcript in pig urethra. Caffeine (> or =3 mM) inhibited the channel activity of Kir6.2DeltaC36 expressed in COS7 cells (3 mM caffeine, 65+/-6%, n=4; 10 mM caffeine, 29+/-2%, n=4). These results suggest that caffeine can inhibit the activity of K(ATP) channels through a direct blocking effect on the pore-forming Kir subunit.
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PMID:The effects of caffeine on ATP-sensitive K(+) channels in smooth muscle cells from pig urethra. 1101 1

We previously described the isolation of yeast mutants (sex mutants) that secrete reduced amounts of mature alpha-factor when it is synthesized as part of a fusion with prosomatostatin. In the present study we show that the sex3-1 mutant displays pleiotropic phenotypes. These include an abnormal morphology, an osmoremediable caffeine sensitivity, reduced secretion of mature alpha-factor, a weakened cell wall and a marked deficiency in halotolerance. Cloning of the SEX3 gene revealed that it is identical to the RPB4 gene. This gene encodes the fourth largest subunit of yeast RNA polymerase II, which has been postulated to play a major role in the response to stress. We show that transcriptional activation in response to either a cell wall stress or to growth in the presence of elevated salt concentrations is minimally affected by the loss of RPB4 function. However, whereas the levels of several mRNAs are similarly reduced (by about 30%) in rpb4 mutants grown in rich medium at moderate temperature, some transcripts, in particular ZDS1, are more abundant. An increase dosage of ZDS1, or of genes involved in cell wall assembly and in secretion (RHO1 and SR077, respectively), partially suppresses the sensitivity of rpb4delta cells to high temperature, heat shock and stationary phase. Collectively, our results indicate that the loss of Rpb4p perturbs several cellular functions that contribute to the inappropriate stress response of rpb4delta yeast. We therefore conclude that this RNA poiymerase II subunit is not specifically involved in the stress response.
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PMID:Multiple cellular processes affected by the absence of the Rpb4 subunit of RNA polymerase II contribute to the deficiency in the stress response of the yeast rpb4(delta) mutant. 1125 23

Kluyveromyces lactis killer strains secrete a zymocin complex that inhibits proliferation of sensitive yeast genera including Saccharomyces cerevisiae. In search of the putative toxin target (TOT), we used mTn3:: tagging to isolate zymocin-resistant tot mutants from budding yeast. Of these we identified the TOT1, TOT2 and TOT3 genes (isoallelic with ELP1, ELP2 and ELP3, respectively) coding for the histone acetyltransferase (HAT)-associated Elongator complex of RNA polymerase II holoenzyme. Other than the typical elp ts-phenotype, tot phenocopies hypersensitivity towards caffeine and Calcofluor White as well as slow growth and a G(1) cell cycle delay. In addition, TOT4 and TOT5 (isoallelic with KTI12 and IKI1, respectively) code for components that associate with ELONGATOR: Intriguingly, strains lacking non-Elongator HATs (gcn5, hat1, hpa3 and sas3) or non-Elongator transcription elongation factors TFIIS (dst1) and Spt4p (spt4) cannot confer resistance towards the K.lactis zymocin, thus providing evidence that Elongator equals TOT and that Elongator plays an important role in signalling toxicity of the K.lactis zymocin.
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PMID:Saccharomyces cerevisiae Elongator mutations confer resistance to the Kluyveromyces lactis zymocin. 1129 32


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