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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Trypanosoma brucei mitochondrial transcripts can be posttranscriptionally processed by uridine addition or deletion. With editing of mRNAs, uridine addition and deletion create precisely altered reading frames. The addition of nonencoded uridines to mitochondrial guide RNAs results in a less precise modification. Although uridines are specifically added to the 3' termini, their number varies, which results in heterogeneous oligo(U) tails on guide RNAs. In this paper, we show that the mitochondrial 9S and 12S rRNAs are also modified by uridine addition. These modifications appear to have aspects in common with both RNA editing and oligo(U) tail formation. Metabolic labeling studies with intact mitochondria and [alpha-32P]UTP, in the absence of transcription, demonstrated the posttranscriptional timing of the event. T1 RNase comparison analyses of cytidine 3',5'-[5'-32P]biphosphate 3'-end-labeled and [alpha-32P]UTP metabolically labeled rRNAs, along with direct RNA sequencing of the 3' termini, identified the site of uridine addition and revealed the creation of an oligo(U) tail for both rRNAs. 12S and 9S rRNAs hybrid selected from total cell RNA exhibited the same modification, demonstrating the presence of this processing in vivo. Moreover, only 3'-poly(U)-tailed 9S and 12S rRNAs were detected in total cellular and mitochondrial RNAs, which suggests that they are the most abundant and probable mature forms. The 12S and 9S rRNA oligo(U) tails differed significantly from each other, with the 12S having a heterogeneous tail of 2 to 17 uridines and the 9S having a tail of precisely 11 uridines. The mechanism of formation and the function of the rRNA poly(U) tails remain to be determined.
Mol Cell Biol 1991 Dec
PMID:Modification of Trypanosoma brucei mitochondrial rRNA by posttranscriptional 3' polyuridine tail formation. 171 73

In order to study the effects of trans-acting factors on cis-acting elements in plant genes an in vitro reinitiating nuclear transcription system is needed. Here we report that run-on experiments with nuclei isolated from 2,4-D-treated auxin-starved early-stationary-phase cells of tobacco clearly show reitintiation of transcription of specific 2,4-D-induced genes. Using gamma-thio nucleotides and [alpha-32P]-UTP we were able to demonstrate the presence of reinitiated labelled specific RNAs after isolation on a mercury-agarose affinity column. Addition of heparin as an inhibitor blocked this reinitiation. In a primer extension assay we found that the new transcripts initiate at approximately the same site as used in vivo.
Plant Mol Biol 1992 Jan
PMID:Specific transcription and reinitiation of 2,4-D-induced genes in tobacco nuclei. 173 62

In situ hybridization was used to localize the cells that express the estradiol receptor gene (ER) in the forebrain (hypothalamus, preoptic area, telencephalon) of the rainbow trout (Oncorhynchus mykiss). Both sense and anti-sense [35S]UTP-labeled single-stranded RNA probes were generated from the estradiol binding domain of the ER cDNA. The sense probe was used to evaluate the background of the hybridization reaction. In the forebrain, specific signal appeared in three areas: the posterior hypothalamus, the preoptic area, and the ventral telencephalon. Our localization correlates with [3H]estradiol binding studies in other teleost species. In the pituitary, we observed a weak signal when compared to the signal observed in the forebrain (about ten grains/cell in the pituitary against 35 grains/cell in the posterior hypothalamus). A significant difference was also observed between the intensity of labeling per cell when different forebrain nuclei were compared. We provide here evidence for a tissue-specific regulation of the ER mRNA levels in the trout hypothalamo-pituitary axis.
Mol Cell Endocrinol 1991 Apr
PMID:Localization of the estradiol receptor mRNA in the forebrain of the rainbow trout. 182 Sep 72

The influence of an increased temperature (39 degrees C) on a denaturation of 50 kDa-fragment of myosin subfragment 1 was studied in the presence of different nucleoside triphosphates (NTP) and nucleoside diphosphates (NDP). The degree of the denaturation was appreciated evaluated from its trypsinolysis depth. According to their protective influence NTP and NDP were shown to arrange in lines ATP greater than or equal to CTP greater than UTP greater than GTP and ADP greater than GDP greater than CDP greater than UDP, correspondingly. The results received and the literature data allow to suggest that there are at least two states of ATPase site hydrophobic pocket, one of which in responsible for sharp ATPase reaction slowing-down on the stage of macroergic bonding splitting.
Mol Biol (Mosk)
PMID:[Functionally different states of the "hydrophobic pocket" of the myosin ATPase center]. 183 76

The purified Ca2+/Mg2+ ATPase from rat heart plasma membrane was activated by Ca2+ and Mg2+ with Ka values of 1.47 mM and 2.51 mM, respectively; other divalent cations also activated the enzyme but to a lesser extent. Divalent cations like Cu2+, Zn2+, Ni2+, Cd2+ were potent inhibitors of the enzyme activity in the presence of Ca2+ or Mg2+ whereas Na+, K+ or HCO3- did not affect the Ca2+/Mg2+ ATPase activity; the pH optima was 8.5. The enzyme hydrolyzed ATP with a Km of 0.34 mM for Ca2+ ATPase and 0.48 mM for Mg2+ ATPase; various nucleoside triphosphate such as ITP, CTP, GTP, and UTP were also hydrolyzed. Phospholipase A and C as well as neuraminidase decreased the Ca2+/Mg2+ ATPase activity whereas phospholipase D was ineffective. The purified Ca2+/Mg2+ ATPase was found to bind ATP-r-35S with two affinities; the KD values were 50.9 +/- 0.8 and 1160 +/- 198 nM and the Bmax values were 8.71 +/- 0.16 and 145 +/- 9.7 nmol/mg protein for high and low affinity sites, respectively. Treatment of the enzyme preparation with phospholipases and neuraminidase did not affect the ATP-r-35S binding. Ca2+ was also found to bind with Ca2+/Mg2+ ATPase with a KD of 0.384 mM and a Bmax of 1.85 mumol/mg protein; Ni2+, Mn2+, Zn2+ at 1 mM concentrations inhibited the Ca2+ binding but Mg2+ and verapamil were without effect. Phospholipase A and neuraminidase decreased the Ca2+ binding by 20-30%; this indicated that Ca2+ binding with the purified enzyme may be partly due to the phospholipids and sialic acid residues associated with the enzyme. These results show that the purified Ca2+/Mg2+ ATPase is a Ca2+ binding glycoprotein having two binding sites for ATP. Furthermore, this study suggests that phospholipids associated with purified Ca2+/Mg2+ ATPase are required for maximal activity.
Mol Cell Biochem 1991 Oct 16
PMID:Characterization of the purified rat heart plasma membrane Ca2+/Mg2+ ATPase. 183 90

Primary cultures of neonatal cardiac myocytes were used to determine the effects of tumor-promoting phorbol esters on ribosomal RNA (rRNA) synthesis during myocyte growth. Treatment of myocytes with phorbol-12, 13-dibutyrate (PDBu) increased protein accumulation by 25% and RNA content by 20%. Rates of rRNA synthesis were measured to assess the mechanism by which rRNA accumulated during myocyte growth. Rates of rRNA synthesis were determined from the incorporation of [3H]uridine into UMP of purified rRNA and the specific radioactivity of the cellular UTP pool. After 24h of PDBu treatment, cellular rates of 18S and 28S rRNA synthesis were accelerated by 67% and 64%, respectively. The increased rate of rRNA synthesis accounted for the net increase in myocyte rRNA content after PDBu treatment.
Mol Cell Biochem
PMID:Stimulation of ribosomal RNA synthesis during hypertrophic growth of cultured heart cells by phorbol ester. 192 97

Extracellular ATP and UTP produced a rapid accumulation of inositol phosphates in human airway epithelial cells (CF/T43). The order of agonist potencies for a series of nucleotide analogues differed markedly from that of the classically described P2x- or P2y-purinergic receptors. UTP was the most potent agonist and was fully efficacious; ATP and adenosine-5'-O-(3-thiotriphosphate) were also full agonists. In contrast, 2-methylthio-ATP, adenosine-5'-O-(2-thiodiphosphate) and alpha,beta-methylene-ATP were without effect. ADP and UDP had little or no effect at concentrations as high as 100 microM, and deoxyribose and dideoxyribose compounds were inactive. The effects of ATP and UTP were not additive, whereas bradykinin- or histamine-stimulated inositol phosphate production was additive with the effects of ATP or UTP. Preincubation of cells with either UTP or ATP resulted in a parallel loss of responsiveness to both agonists. Desensitization was specific for the response to nucleotides, because no ATP- or UTP-induced effect on the response to histamine or bradykinin was observed. Pertussis toxin treatment of CF/T43 cells produced a 30-40% decrease in the response to ATP or UTP, which correlated with the ADP-ribosylation of 41- and 43-kDa proteins. Bradykinin and histamine responses were not modified by pertussis toxin. Guanine nucleotides had little effect on the inositol phosphate response in intact CF/T43 cells at concentrations below 100 microM. However, in streptolysin-O-permeabilized cells GTP-gamma S produced a concentration-dependence activation of inositol phosphate formation. UTP or ATP had little effect in permeabilized cells in the absence of guanine nucleotides but markedly increased inositol phosphate formation in the presence of guanine nucleotides. Taken together, these results suggest that UTP and ATP activate a 5'-nucleotide receptor on CF/T43 cells that is distinct from the classically defined P2x- and P2y-purinergic receptors. Activation of phospholipase C by this receptor involves, at least in part, a guanine nucleotide-binding regulatory protein.
Mol Pharmacol 1991 Nov
PMID:Evidence that UTP and ATP regulate phospholipase C through a common extracellular 5'-nucleotide receptor in human airway epithelial cells. 194 36

Chloroquine susceptibility and resistance have been associated respectively with the uptake and efflux of chloroquine by Plasmodium falciparum. We made membrane preparations from parasitized and unparasitized red cells in order to study chloroquine accumulation in a cell-free system. The accumulation of [3H]chloroquine by these preparations is inhibited by unlabeled chloroquine and thus is specific. Only membranes from parasitized red cells demonstrate time-dependent chloroquine accumulation; membranes from unparasitized red cells do not. Chloroquine accumulation is eliminated by detergent (0.05% Triton X-100) and reduced by a hypertonic medium, consistent with accumulation inside membrane vesicles rather than binding to membranes. Accumulation is energy dependent; it has a specific requirement for ATP, which cannot be replaced with GTP, CTP, UTP, TTP or ADP, an apparent Km of 21 microM and an apparent Vmax of 4.6 pmol (mg protein)-1 h-1. Vesicle acidification is MgATP dependent, and is reversed by NH4Cl. Chloroquine accumulation is inhibited by reduced medium pH, N-ethylmaleimide or oligomycin, but not by vanadate or ouabain. These studies demonstrate that membrane vesicles prepared from parasitized red cells provide a model system for the study of chloroquine accumulation by P. falciparum.
Mol Biochem Parasitol
PMID:Accumulation of chloroquine by membrane preparations from Plasmodium falciparum. 214 9

The effects of hyperbaric oxygen on uracil nucleotide metabolism in B104 rat neuroblastoma cells were investigated. Cells exposed to 10 atm O2 for 4 h incorporated markedly less [3H]uridine into the acid-soluble fraction and RNA compared to cells kept in ambient air. The acid-soluble fraction of the oxygen-treated cells contained less total [3H]uridine phosphates ([3H]UMP + [3H]UDP + [3H]UTP) than air-treated cells. Uridine kinase activity, assayed in cytosolic extracts from cells exposed to 10 atm O2 for 4 h, was decreased by 46% compared to the air controls. The reduced enzyme activity which appears to account for the depressed [3H]uridine incorporation, may contribute to the lethal effects of oxygen in these cells.
Mol Cell Biochem 1990 Jun 01
PMID:Adverse effects of hyperbaric oxygen on [3H]uridine incorporation and uridine kinase activity in B104 rat neuroblastoma cells. 216 39

Purines and purine nucleotides were found to affect transcription of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene in whole nuclei isolated from intestinal mucosa of adult rats fed a purine- and purine nucleotide-free diet. Nuclear run-on transcription assays, performed on whole nuclei from different tissues and cell types, identified an intestine-specific decrease in the overall incorporation of [alpha-32P]UTP in HPRT transcripts from intestinal epithelial cell nuclei when exogenous purines or purine nucleotides were omitted from either the diet or culture medium. Using a 990-base-pair genomic fragment that contains the 5'-flanking region from the HPRT gene, we generated plasmid constructs with deletions, transfected the DNA into various cell types, and assayed for chloramphenicol acetyltransferase (CAT) reporter activity in vitro. We determined that an element upstream from the putative transcriptional start site is necessary to maintain the regulatory response to purine and nucleotide levels in cultured intestinal epithelial cells. These results were tissue and cell type specific and suggest that in the absence of exogenous purines, the presence of specific factors influences transcriptional initiation of HPRT. This information provides evidence for a mechanism by which the intestinal epithelium, which has been reported to lack constitutive levels of de novo purine nucleotide biosynthetic activity, could maintain and regulate the salvage of purines and nucleotides necessary for its high rate of cell and protein turnover during fluctuating nutritional and physiological conditions. Furthermore, this information may provide more insight into regulation of the broad class of genes recognized by their lack of TATA and CCAAT box consensus sequences within the region proximal to the promoter.
Mol Cell Biol 1990 Aug
PMID:A regulatory element is characterized by purine-mediated and cell-type-specific gene transcription. 237 Aug 69


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