Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

UTP-modulated attenuation of transcription is involved in regulating the synthesis of pyrimidine nucleotides in Escherichia coli. Thus, expression of two genes, pyrBI and pyrE, was shown to be under this type of control. The genes encode the two subunits of aspartate transcarbamylase and orotate phosphoribosyltransferase respectively. The levels of these enzymes are inversely correlated with the intracellular concentration of UTP. Modulation of attenuation seems to be a consequence of the effect of UTP concentration on the mRNA chain growth rate. Reducing the UTP pool retards RNA polymerase movement. Mechanistically this will couple the ribosomes translating a leader peptide gene more tightly to the elongating RNA polymerase. The ribosomes will then be more prone to prevent the folding of the mRNA chains into terminating hairpin structures when RNA polymerase is at the attenuator and has to decide whether transcription should terminate or continue into the structural genes. This paper described a study of pyrBI and pyrE gene regulation in cells where the ribosomes move slowly as a result of mutation in rpsL. It appears that expression of the two genes is hyper-regulated by the UTP pool in this type of cells. Furthermore, the attenuator model can only account for the results if it is assumed that UTP-concentration-dependent pausing of transcription occurs in vivo in the two pyr gene leaders such that RNA polymerase waits for the coupled ribosomes before transcribing into the attenuator regions.
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PMID:Hyper-regulation of pyr gene expression in Escherichia coli cells with slow ribosomes. Evidence for RNA polymerase pausing in vivo? 304 90

Orotate phosphoribosyltransferase (EC 2.4.2.10) was purified to electrophoretic homogeneity from a strain of Escherichia coli containing the pyrE gene cloned on a multicopy plasmid. The relative molecular masses (Mr) of the native enzyme and its subunit were estimated by means of gel filtration and electrophoresis in the presence of dodecyl sulfate. The amino acid sequences at the N and C termini, as well as the amino acid composition, were determined. The nucleotide sequence of the structural pyrE gene, including 394 nucleotide residues preceding the beginning of the coding frame, was also established. From the results the following conclusions may be drawn. Orotate phosphoribosyltransferase is a dimeric protein with subunits of Mr 23 326 consisting of 211 amino acid residues. The pyrE gene is transcribed in a counter-clock wise direction from the E. coli chromosome as an mRNA with a considerable leader segment in front of the protein-coding region. This leader contains a structure with features characteristic for a (translated?) rho-independent transcriptional terminator, which is preceded by a cluster of uridylate residues. This indicates that the frequency of pyrE transcription is regulated by an RNA polymerase (UTP) modulated attenuation.
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PMID:Nucleotide sequence of the Escherichia coli pyrE gene and of the DNA in front of the protein-coding region. 634 99

A mutant of Salmonella typhimurium with a defect in the regulation of pyr-gene expression was obtained during a selection for mutants resistant to a combination of the two pyrimidine analogs, 5-fluorouracil and 5-fluorouridine. The mutant possesses 4-fold elevated pools of the pyrimidine nucleoside triphosphatases, UTP and CTP. The specific activities of aspartate transcarbamylase and orotate phosphoribosyltransferase are 40-fold and 7-fold higher in the mutant than in the parent strain when grown in minimal media. Furthermore, the synthesis of the two enzymes in the mutant is not repressed following addition of exogenous pyrimidines. The levels of carbamoylphosphate synthase and orotidine 5'-monophosphate decarboxylase are approximately 3-fold enhanced, while the activities of dihydroorotase and dihydroorotate oxidase appear largely unaffected by the mutation. The mutation responsible for these effects was shown to map between two known point mutations in the rpoBC gene cluster encoding the beta and beta' subunits of RNA polymerase. These observations indicate a regulatory function of RNA polymerase in the control of pyr-gene expression in S. typhimurium.
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PMID:RNA polymerase involvement in the regulation of expression of Salmonella typhimurium pyr genes. Isolation and characterization of a fluorouracil-resistant mutant with high, constitutive expression of the pyrB and pyrE genes due to a mutation in rpoBC. 676 70

We have cloned genes encoding three enzymes of the de novo pyrimidine pathway using genomic DNA from Plasmodium falciparum and sequence information from the Malarial Genome Project. Genes encoding dihydroorotase (reaction 3), orotate phosphoribosyltransferase (reaction 5), and OMP decarboxylase (reaction 6) have been cloned into the plasmid pET 3a or 3d with a thrombin cleavable 9xHis tag at the C-terminus and the enzymes were expressed in Escherichia coli. To overcome the toxicity of malarial OMP decarboxylase when expressed in E. coli, and the unusual codon usage of the malarial gene, a hybrid plasmid, pMICO, was constructed which expresses low levels of T7 lysozyme to inhibit T7 RNA polymerase used for recombinant expression, and extra copies of rare tRNAs. Catalytically-active OMP decarboxylase has been purified in tens of milligrams by chromatography on Ni-NTA. The gene encoding orotate phosphoribosyltransferase includes an extension of 66 amino acids from the N-terminus when compared with sequences for this enzyme from other organisms. We have found that other pyrimidine enzymes also contain unusual protein inserts. Milligram quantities of pure recombinant malarial enzymes from the pyrimidine pathway will provide targets for development of novel antimalarial drugs.
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PMID:Cloning and expression of malarial pyrimidine enzymes. 1557 Dec 77

Novel N-1-sulfonylpyrimidine derivatives have a strong antiproliferative activity and an ability to induce apoptosis in treated tumor cells. The purpose of this study was to elucidate the effects of two N-1-sulfonylpyrimidine nucleobases on catalytic activity of tumor cells' enzymes involved in DNA and RNA synthesis, and in de novo and salvage pyrimidine and purine syntheses. Investigations were performed in vitro on colon carcinoma cells (Caco2). The biosynthetic activity of the tumor cells' enzymes was determined using sensitive radio-assays. Enzyme activity in treated cells was calculated relative to untreated control cells. Both of the investigated compounds, 1-(p-toluenesulfonyl) cytosine (TsC) and 5-bromo-1-(methanesulfonyl) uracil (BMsU) inhibited activities of specific enzymes involved in nucleic acid synthesis. BMsU strongly inhibited activities of DNA polymerase alpha (53%), thymidine kinase (68%), thymidilate synthase (43%), and ribonucleotide reductase (46%). De novo biosynthesis of pyrimidine and purine was reduced by 20%. TsC was able to inhibit RNA polymerase (37%), orotate phosphoribosyltransferase (39%), uridine kinase (44%), ribonucleotid reductase (47%), and de novo purine synthesis (61%). Antitumor activity of 1-(p-toluenesulfonyl) cytosine (TsC) and 5-bromo-1-(methanesulfonyl) uracil (BMsU) is closely associated with their inhibitory activity on enzymes that play an important role in the metabolism of tumor cells.
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PMID:Metabolic effects of novel N-1-sulfonylpyrimidine derivatives on human colon carcinoma cells. 1591 14

Thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), thymidine phosphorylase (TP), and orotate phosphoribosyltransferase (OPRT) have been reported to be predictive parameters for the efficacy of fluoropyrimidine-based chemotherapy. mRNA expression of TS, DPD, TP, and OPRT were quantified by reverse-transcriptase polymerase chain reaction after harvesting cancer cells from 93 paraffin-embedded specimens of gastric cancer through laser capture microdissection. In vitro chemosensitivity testing by histoculture drug response assay was performed with surgically resected primary lesions of the same 93 patients. No significant correlation was observed between the mRNA expression and location of the tumor, histopathologic type, clinical stage, and other clinicopathologic variables, with the exception that OPRT mRNA had a weak correlation with drug sensitivity against 5FU (R=0.219, p=0.0343). OPRT was considered to have a major impact on drug sensitivity, although not sufficiently so to enable prediction of 5FU sensitivity solely based on the mRNA expression of this enzyme.
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PMID:Gene expression of 5-fluorouracil metabolic enzymes in primary gastric cancer: correlation with drug sensitivity against 5-fluorouracil. 1730 23