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)

Formation of complex I between phage f2 RNA and coat protein, leading to repression of phage RNA polymerase synthesis, depends nonlinearly upon the concentration of the coat protein. Maximum formation of complex I was observed when six molecules of coat protein were bound to one molecule of RNA. RNase digestion of a glutaraldehyde-fixed complex left, as the products, coat protein oligomers. The heaviest, hexamers, predominated in the mixture. It was also shown that, in an ionic environment required for phage protein synthesis, coat protein at a concentration optimum for complex I formation exists in solution as a dimer. The results indicate that the translational repression of the RNA polymerase cistron is due to a cooperative attachment to phage template of three dimers of coat protein, forming a hexameric cluster on an RNA strand.
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PMID:Hexamer of bacteriophage f2 coat protein as a repressor of bacteriophage RNA polymerase synthesis. 80 44

The NADH dehydrogenase subunit A (ndhA) gene from maize chloroplasts encodes a highly conserved peptide, which at several positions could be restored to consensus sequences by potential C-to-U editing of the codons involved. This gene was, therefore, chosen for analysis of its mRNA sequence in the form of amplified cDNA. A comparison of this cDNA sequence with the plastome-encoded ndhA sequence reveals four C-to-U editing sites, thereby demonstrating as a novel finding that chloroplast editing can also affect internal mRNA positions. All the edited codons restore amino acids that are conserved in the ndhA-encoded peptides of other chloroplast species. Alignment with homologous mitochondrial NADH-ubiquinone reductase subunit 1 (nad1) sequences of plant and even nonplant species shows that two of the editing positions restore universally conserved amino acids and that one editing site is even shared with nad1 mRNA of plant mitochondria. No editing sites could be detected in the cDNA derived from transcripts of the maize chloroplast RNA polymerase alpha-subunit (rpoA) gene.
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PMID:Internal editing of the maize chloroplast ndhA transcript restores codons for conserved amino acids. 149 12

In HeLa cells, RNA polymerase III (pol III)-mediated transcription is severely inhibited by poliovirus infection. This is due primarily to a reduction in the transcriptional activity of TFIIIC, a transcription factor which binds in a sequence specific manner to the internal promoter of pol III genes. Using gel retardation assays, we have shown previously that inhibition of pol III transcription by poliovirus is correlated with disappearance of a transcriptionally active form of TFIIIC (complex I) concomitant with the appearance of a faster mobility, transcriptionally inactive form of TFIIIC (complex III). We show here that a poliovirus with a point mutation in the proteinase 3C (3Cpro) region failed to produce complex III and is limited in its ability to inhibit pol III transcription compared with the wild-type virus. Incubation of purified 3Cpro, expressed in Escherichia coli, with transcriptionally active TFIIIC (complex I) in vitro resulted in generation of the transcriptionally inactive complex III form of TFIIIC. In an in vitro transcription assay, treatment of the complex I form of TFIIIC with 3Cpro almost completely inhibited pol III transcription. Finally expression of the 3Cpro gene in transfected HeLa cells resulted in significant inhibition of pol III-mediated transcription. The results presented here suggest that proteolysis of the transcriptionally active form of TFIIIC by poliovirus 3Cpro is a mechanism by which poliovirus inhibits host cell RNA pol III transcription.
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PMID:Poliovirus proteinase 3C converts an active form of transcription factor IIIC to an inactive form: a mechanism for inhibition of host cell polymerase III transcription by poliovirus. 191 71

In HeLa cells, RNA polymerase III (pol III)-mediated transcription is severely inhibited by poliovirus infection. This inhibition is due primarily to the reduction in transcriptional activity of the pol III transcription factor TFIIIC in poliovirus-infected cells. However, the specific binding of TFIIIC to the VAI gene B-box sequence, as assayed by DNase I footprinting, is not altered by poliovirus infection. We have used gel retardation analysis to analyze TFIIIC-DNA complexes formed in nuclear extracts prepared from mock- and poliovirus-infected cells. In mock-infected cell extracts, two closely migrating TFIIIC-containing complexes, complexes I and II, were detected in the gel retardation assay. The slower migrating complex, complex I, was absent in poliovirus-infected cell extracts, and an increase occurred in the intensity of the faster-migrating complex (complex II). Also, in poliovirus-infected cell extracts, a new, rapidly migrating complex, complex III, was formed. Complex III may have been the result of limited proteolysis of complex I or II. These changes in TFIIIC-containing complexes in poliovirus-infected cell extracts correlated kinetically with the decrease in TFIIIC transcriptional activity. Complexes I, II, and III were chromatographically separated; only complex I was transcriptionally active and specifically restored pol III transcription when added to poliovirus-infected cell extracts. Acid phosphatase treatment partially converted complex I to complex II but did not affect the binding of complex II or III. Dephosphorylation and limited proteolysis of TFIIIC are discussed as possible mechanisms for the inhibition of pol III-mediated transcription by poliovirus.
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PMID:A transcriptionally active form of TFIIIC is modified in poliovirus-infected HeLa cells. 220 7

We have determined the complete nucleotide sequence of chloroplast DNA from a liverwort, Marchantia polymorpha, using a clone bank of chloroplast DNA fragments. The circular genome consists of 121,024 base-pairs and includes two large inverted repeats (IRA and IRB, each 10,058 base-pairs), a large single-copy region (LSC, 81,095 base-pairs), and a small single-copy region (SSC, 19,813 base-pairs). The nucleotide sequence was analysed with a computer to deduce the entire gene organization, assuming the universal genetic code and the presence of introns in the coding sequences. We detected 136 possible genes. 103 gene products of which are related to known stable RNA or protein molecules. Stable RNA genes for four species of ribosomal RNA and 32 species of tRNA were located, although one of the tRNA genes may be defective. Twenty genes encoding polypeptides involved in photosynthesis and electron transport were identified by comparison with known chloroplast genes. Twenty-five open reading frames (ORFs) show structural similarities to Escherichia coli RNA polymerase subunits, 19 ribosomal proteins and two related proteins. Seven ORFs are comparable with human mitochondrial NADH dehydrogenase genes. A computer-aided homology search predicted possible chloroplast homologues of bacterial proteins; two ORFs for bacterial 4Fe-4S-type ferredoxin, two for distinct subunits of a protein-dependent transport system, one ORF for a component of nitrogenase, and one for an antenna protein of a light-harvesting complex. The other 33 ORFs, consisting of 29 to 2136 codons, remain to be identified, but some of them seem to be conserved in evolution. Detailed information on gene identification is presented in the accompanying papers. We postulated that there were 22 introns in 20 genes (8 tRNA genes and 12 ORFs), which may be classified into the groups I and II found in fungal mitochondrial genes. The structural gene for ribosomal protein S12 is trans-split on the opposite DNA strand. The universal genetic code was confirmed by the substitution pattern of simultaneous codons, and by possible codon recognition of the chloroplast-encoded tRNA molecules, assuming no importation of tRNA molecules from the cytoplasm. The nucleotide residue A or T is preferred at the third position of the codons (G+C, 11.9%) and in intergenic spacers (G+C, 19.5%), resulting in an overall G+C content that is low (28.8%) throughout the liverwort chloroplast genome. Possible gene expression signals such as promoters and terminators for transcription, predicted locations of gene products, and DNA replicative origins are discussed.
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PMID:Structure and organization of Marchantia polymorpha chloroplast genome. I. Cloning and gene identification. 246 54

The nucleotide sequence (56,410 base-pairs) of the large single-copy region of chloroplast DNA from the liverwort Marchantia polymorpha has been determined. The sequence starts from one end (JLA) of the large single-copy region and encompasses genes for 21 tRNAs, six ATPase subunits (atpA, atpB, atpE, atpF, atpH and atpI), two photosystem I polypeptides (psaA and psaB), four photosystem II polypeptides (psbA, psbC, psbD and psbG), five ribosomal proteins (rps2, rps4, rps7, rps'12 and rps14), and three RNA polymerase subunits (rpoB, rpoC1 and rpoC2). In addition, we detected 18 open reading frames ranging from 29 to 2136 amino acid residues long, four of which share significant amino acid sequence homology to those of an Escherichia coli malK protein (designated mbpX), human mitochondrial ND2 (ndh2) and ND3 (ndh3) of a respiratory chain NADH dehydrogenase, or a bacterial antenna protein of a light-harvesting complex (lhcA). Sequence analysis suggests that four tRNA genes and six protein genes might be split by introns; they are trnG(UCC), trnK(UUU), trnL(UAA), trnV(UAC), atpF, ndh2, rpoC1, rps'12, ORF135 and ORF167. In the large single-copy region described here, the gene organization deduced is highly conserved with respect to that of higher plants, but an inversion of some 30,000 base-pairs flanked by trnL(CAA) and trnD(GUC) was seen between the liverwort and tobacco chloroplast genomes.
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PMID:Structure and organization of Marchantia polymorpha chloroplast genome. II. Gene organization of the large single copy region from rps'12 to atpB. 297 85

The bactericidal activity of Tinopal AN [1,1-bis(3,N-5-dimethyl-benzoxazol-2-yl)-methine p-toluene sulphonate] was shown to be due to a mechanism entirely independent of its inhibitory effects upon NADH dehydrogenase which were reported previously. Whereas the compound had no significant effect upon DNA synthesis in Escherichia coli D22, RNA and protein synthesis were immediately and markedly inhibited. In confirmation, Tinopal AN caused an immediate cessation in inducible beta-galactosidase synthesis in the same organism. An in vitro assay of the transcription of calf-thymus DNA by purified E. coli RNA polymerase showed that this process was inhibited by Tinopal AN.
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PMID:The antibacterial action of Tinopal AN. 620

FNR is a transcriptional regulator that controls gene expression in response to oxygen limitation in Escherichia coli. The NADH dehydrogenase II gene (ndh) is repressed by FNR under anaerobic conditions. Repression is not simply due to occlusion of the promoter (-35 and -10) region by FNR because adjacent pairs of FNR monomers were found to bind at two sites centred at -50.5 and -94.5 in the ndh promoter region without preventing RNA polymerase binding. However, contact between RNA polymerase and the -132 to -62 region of the non-coding strand of ndh DNA, and RNA polymerase-mediated open complex formation, were prevented by bound FNR. The upstream FNR-binding site (-94.5) was needed for efficient FNR-dependent repression of ndh transcription in vitro, and also for repression of an ndh-lacZ fusion in vivo. Anaerobic ndh repression may thus involve the binding of two pairs of FNR monomers upstream of the -35 region, which prevents essential RNA polymerase-DNA contacts in the upstream region as well as inhibiting RNA polymerase function by direct FNR interaction. Expression of the ndh-lacZ fusion in an fnr deletion strain was enhanced by anaerobic growth in rich medium or minimal medium supplemented with amino acids. Furthermore, two proteins (M(r) 12,000 and 35,000) which interact with and may activate transcription from the ndh promoter under these conditions were detected by gel retardation analysis. These putative amino acid-responsive activators may thus offset FNR-mediated repression and maintain a low level of anaerobic ndh expression for regulating the NAD+/NADH ratio during growth in rich media.
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PMID:Regulation of transcription at the ndh promoter of Escherichia coli by FNR and novel factors. 806 61

The ndh gene that encodes the non-proton-translocating NADH dehydrogenase II of Escherichia coli is anaerobically repressed by FNR. However, in the absence of FNR, ndh expression is enhanced by anaerobic growth in media containing amino acids. Two potential regulatory proteins that may be associated with this activation have previously been detected, Arr (amino acid response regulator) and Nbp (ndh-binding protein). Studies with the heat-stable Nbp have now shown that it is present in E. coli grown both aerobically and anaerobically in rich and minimal media, indicating that it is not specifically associated with the anaerobic enhancement of ndh expression. The Nbp activity of aerobic cultures was maximal during exponential growth phase (when ndh promoter activity is minimal) but fell rapidly as cultures entered stationary phase and ndh expression increased. Protein purification and mutant studies have further shown that Nbp is identical to the Fis protein (factor for inversion stimulation). Three major and two minor Nbp (Fis)-binding sites have been identified in the ndh promoter by gel retardation and DNase I footprinting. The major sites are centred at -123, -72 and +51, in decreasing order of binding affinity. At low concentrations, Nbp (Fis) increased transcription from the ndh promoter by up to 25%, whereas at higher concentrations it prevented RNA polymerase (RNAP) binding and open complex formation. Consequently, Nbp (Fis) can both activate and repress transcription from the ndh promoter. The results suggest that Nbp (Fis) serves to ensure that the energetically efficient proton-translocating NADH dehydrogenase I is used in preference to the non-proton translocating NADH dehydrogenase II during periods of rapid growth, by repressing expression of the ndh gene.
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PMID:The ndh-binding protein (Nbp) regulates the ndh gene of Escherichia coli in response to growth phase and is identical to Fis. 880 57

The ndh gene of Escherichia coli encodes a non-proton-translocating NADH dehydrogenase (NdhII) that is anaerobically repressed by the global transcription regulator, FNR. FNR binds at two sites (centred at -50.5 and -94.5) in the ndh promoter but the mechanism of FNR-mediated repression appears not to be due to promoter occlusion. This mechanism has been investigated using an aerobically active derivative of FNR, FNR* (FNR-D154A), with ndh promoters containing altered FNR-binding sites. FNR* repressed ndh gene expression both aerobically and anaerobically in vivo. Gel retardation analysis and DNase I footprinting with purified FNR* protein confirmed that FNR interacts at two sites in the ndh promoter, and that FNR and RNA polymerase (RNAP) can bind simultaneously. Studies with three altered ndh promoters, each containing an impaired or improved FNR-site, indicated that both FNR-sites are needed for efficient repression in vivo. The alpha-subunit of RNAP interacted with two regions (centred at -105 and -46), each overlapping one of the FNR-sites in the ndh promoter. Footprints of the FNR*-RNAP-ndh ternary complex indicated that FNR*-binding at -50.5 prevents the alpha-subunit of RNAP from docking with the DNA just upstream of the -35 element. Binding of a second FNR* molecule at the -105 site likewise prevents binding of the alpha-subunit at its alternative site, thus providing a plausible mechanism for FNR-mediated repression based on displacement of the alpha-subunit of RNAP.
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PMID:FNR-dependent repression of ndh gene expression requires two upstream FNR-binding sites. 916 2


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