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)

Various F' plasmids of Escherichia coli K-12 could be transferred into mutants of the soil strain 6.2, classified herein as a Pseudomonas fluorescens biotype IV. This strain was previously found to receive Flac plasmid (N. Datta and R.W. Hedges, J. Gen Microbiol. 70:453-460, 1972). ilv, leu, met, arg, and his auxotrophs were complemented by plasmids carrying isofunctional genes; trp mutants were not complemented or were very poorly complemented. The frequency of transfer was 10(-5). Subsequent transfer into other P. fluorescens recipients was of the same order of magnitude. Some transconjugants were unable to act as donors, and these did not lose the received information if subcultured on nonselective media. Use of F' plasmids helped to discriminate metabolic blocks in P. fluorescens. In particular, metA, metB, and argH mutants were so distinguished. In addition, F131 plasmid carrying the his operon and a supD mutation could partially relieve the auxotrophy of thr, ilv, and metA13 mutants, suggesting functional expression of E. coli tRNA in P. fluorescens. In P. fluorescens metA Rifr mutants carrying the F110 plasmid, which carried the E. coli metA gene and the E. coli rifs allele, sensitivity to rifampin was found to be dominant at least temporarily over resistance. This suggests interaction of E. coli and P. fluorescens subunits of RNA polymerase. his mutations were also complemented by composite P plasmids containing the his-nif region of Klebsiella pneumoniae (plasmids FN68 and RP41). nif expression could be detected by acetylene reduction in some his+ transconjugants. The frequency of transfer of these P plasmids was 5 X 10(-4).
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PMID:F'-plasmid transfer from Escherichia coli to Pseudomonas fluorescens. 9 67

The DNA sequence of 178 base pairs preceding the first structural gene of the threonine operon of Escherichia coli has been determined. A region of perfect 2-fold rotational symmetry, involving 28 base pairs, precedes the first structural gene. The structural similarity of this sequence to known RNA polymerase termination sites suggests that this region is the termination site of the threonine operon leader RNA. Moreover a mutation (thr 79-20), which confers a depressed, constitutive phenotype, was sequenced and found to be a G.C insertion in the putative terminator. A potential coding region for a 21-amino acid leader peptide ends approximately 18 base pairs before the terminator. This peptide contains eight threonine and four isoleucine codons. Eleven of these codons are in tandem. A model for threonine operon regulation, involving alternative secondary RNA structures and translation of leader RNA, is discussed.
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PMID:Regulation of the threonine operon: tandem threonine and isoleucine codons in the control region and translational control of transcription termination. 28 10

A 5789-nucleotide-long EcoRI fragment from the genome of Thermotoga maritima, identified by cross-hybridization to L11, L1, L10, and L12 ribosomal protein gene sequences from Escherichia coli, was cloned and sequenced. The fragment encodes five tRNAs (tRNA(met1), anticodon complementary to AUG; tRNA(met2), AUG; tRNA(thr), ACA; tRNA(tyr), UAC; tRNA(trp), UGG), the transcription termination-antitermination factor nusG, the four 50 S subunit ribosomal proteins L11, L1, L10, and L12, and the amino-terminal portion of the RNA polymerase beta subunit protein. The five tRNA genes, the nusG gene, and the L11, L1, L10, and L12 ribosomal protein genes form a complex transcription unit. Transcripts appear to be initiated from an upstream promoter, P1, located in front of the tRNA(met1) gene and from three internal promoters: P2 is located immediately in front of the tRNA(met2) gene; PL10 is near the beginning of the L1-L10 intergenic space, and PL12 is at the end of the L10 gene sequence. The tRNA sequences are excised from the leader regions of the P1- and P2-initiated transcripts. Three putative but potentially important regulatory sequences were identified within this operon: an L1 translational control site, a transcription attenuator, and a strong rho-independent terminator. The strong terminator located distal to the L12 gene overlaps a fifth promoter, P beta, which is used to initiate transcripts of the downstream RNA polymerase beta subunit gene. The T. maritima NusG protein exhibits 43% amino acid sequence identity when aligned to the E. coli protein; the alignment is interrupted by a large 171-amino acid-long insertion into the T. maritima protein after codon 45.
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PMID:The organization and expression of essential transcription translation component genes in the extremely thermophilic eubacterium Thermotoga maritima. 142 27

We have determined the sequence of cDNA for the human histidyl-tRNA synthetase (HRS) in a hepatoma cell line and confirmed it in fetal myoblast and fibroblast cell lines. The newly determined sequence differs in 48 places, including insertions and deletions, from a previously published sequence. By sequence specific probing and by direct sequencing, we have established that only the newly determined sequence is present in genomic DNA and we have sequenced 500 hundred bases upstream of the translation start site. The predicted amino acid sequence now clearly demonstrates all three motifs recognized in class 2 aminoacyl-tRNA synthetases. Alignment of E. coli, yeast, and when available, mammalian predicted amino acid sequences for three of the four members of the class 2a subgroup (his, pro, ser, and thr) shows strong preservation of amino acid specific signature regions proximal to motif 2 and proximal to motif 3. These probably represent the active site binding regions for the proximal acceptor stem and for the amino acid. The first two exons of human HRS contain a 32 amino acid helical motif, first described in human QRS, a class 1 synthetase, which is found also in a yeast RNA polymerase, a rabbit termination factor, and both bovine and human WRS, suggesting that it may be an RNA binding motif.
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PMID:Human histidyl-tRNA synthetase: recognition of amino acid signature regions in class 2a aminoacyl-tRNA synthetases. 154 69

The E. coli thr operon leader region contains a cluster of transcription pause sites upstream of the attenuator. In this report, we determine the exact sites of pausing and analyze the structure of the ternary complex by footprint techniques. Under synchronized transcription initiation conditions in vitro, three closely-spaced transcription pause sites were identified. These pause sites appeared downstream of the first region of dyad symmetry, which encodes an RNA hairpin in the transcript, and occurred at positions G112, G114 and A116 of the thr leader RNA. The results showed that the half-life of the thr paused complexes at G112 and G114 could be enhanced by limiting the concentration of the nucleoside triphosphate GTP in the transcription reactions. In addition, the half-life of the paused complexes was shown to increase in the presence of NusA protein. The thr leader complex that paused immediately before residues G112 and G114 of the nascent transcript was isolated and its structure was analyzed with enzymatic and chemical cleavage reagents. The footprinting studies using DNase I showed that there were approximately 35 nucleotides on both strands of the DNA that were protected by RNA polymerase from DNase I cleavage. The DNA segment protected by RNA polymerase is approximately 19 nucleotides upstream and 14 nucleotides downstream of the pause sites. The results from hydroxyl radical footprints also showed a similar pattern of protection at the transcription pause sites. However, no significant differences in the footprinting patterns were observed in the presence or absence of NusA protein.
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PMID:Isolation and footprint analysis of the Escherichia coli thr leader paused transcription complex. 170 79

The thr operon of Escherichia coli is regulated by an attenuation mechanism in which regulated transcription termination occurs in response to the levels of charged tRNAthr and tRNAile. Transcription of the thr operon regulatory region in vitro produces a 162-base transcript that is terminated efficiently at the attenuator. The attenuator sequence is similar to other rho-independent terminators. It contains a G + C region of dyad symmetry followed by a run of 9 A + T residues. We have characterized in detail the sequence requirements for efficient transcription termination in vitro. Using a set of point mutations in the G + C region of dyad symmetry of the thr attenuator, we have characterized the effects of these mutations on the efficiency of transcription termination. The efficiency was reduced in all of the mutants analyzed with the greatest effect being an approximate 20% decrease in termination. In some instances the electrophoretic mobilities of the terminated transcripts on 8% polyacrylamide, 8 M urea gels were shifted substantially relative to the wild type-terminated transcript, but the sites of transcription termination were altered by only a few base pairs. We also constructed a set of deletions removing consecutive thymidines which follow the G + C-rich region of dyad symmetry. Removal of 1 or 3 of the 9 thymidine residues had no effect on termination efficiency in vitro or in vivo. Removal of four to six thymidines caused a linear decrease in the efficiency of termination. When only one or two thymidines were present in the template, termination was completely abolished. These results indicate that both the integrity of the RNA stem and the length of the consecutive thymidine residues are important signals recognized by RNA polymerase during transcription of the thr operon regulatory region.
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PMID:Contributions of RNA secondary structure and length of the thymidine tract to transcription termination at the thr operon attenuator. 296 47

Six mutations, impairing DNA polymerase of E. coli in combination with the wild type gene for rho factor or ts-mutation rho 15 have been studied in relation to the expression of seven operons having different types of regulation. The expression of genes for glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase is shown to be constitutive and resistant to mutationally altered RNA polymerase and rho factor. The expression of genes for adenine phosphoribosyltransferase and of deo operon is regulated by rho dependent attenuators with attenuation being lifted incomplete medium. Mutation rho 15 decreases the level of enzymes of thr and lac operons independent of mRNA levels of these operons. Mutation rho 15 effect on posttranscriptional level is modified by mutations damaging RNA polymerase. The data obtained suppose RNA polymerase to affect all stages of realization of genetic information, beginning with promoter recognition and RNA synthesis and including the protein synthesis on mRNA.
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PMID:[Effect of mutation changes in RNA-polymerase and transcription termination factor rho on expression of various operons in E. coli]. 302 82

HpaI restriction analysis of the part of T7 DNA molecule which comes off from E. coli after ultrasonic desorption of virion had been carried out. In such a way it was possible to follow the transfer of labelled T7 DNA into the host cell after the phage adsorption under different conditions. It was established that in the presence of chloramphenicol the left 60% of T7 chromosome is gradually (during 20 min) transferred into the cell and further transport is stopped. This suggests that some T7 gene(s) of I or (and) II class(es) is (are) necessary to transfer the last 40% of T7 DNA molecule containing the genes encoding capsid proteins. Also some new results are obtained which support thr idea about the tight coupling of the processes of T7 DNA transport and its transcription, and about the possibility for RNA polymerase to carry a mechanical function as well. All these results suggest a rather complicated mechanism of the process of T7 DNA transfer into the host cell consisting of at least three stages tightly connected with T7 gene expression temporal control. Some probable consequences of this model as well as its agreement with functional structure of T7 chromosome and with T7 development are discussed.
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PMID:[Discontinuous transfer of phage T7 DNA molecules into Escherichia coli cells during infection]. 704 Sep 43

Allograft rejection is dependent on T cell activation, which requires both the engagement of the T cell receptor by antigen in the context of the MHC molecules and costimulatory signals delivered by cell surface molecules such as B7-CD28/CTLA4 pathway. CTLA4-Ig is a fusion protein that blocks this pathway and has previously been shown to prolong both allograft and xenograft survival. The current study demonstrates markedly prolonged murine cardiac allograft survival and specific prolongation of secondary skin grafts using a combination of CTLA4-Ig plus donor bone marrow. A role for hematopoietic chimerism in the establishment of CTLA4-Ig-induced transplantation tolerance was investigated using reverse transcriptase polymerase chain reaction analysis of recipient tissues. Expression of donor-specific MHC class II transcripts in both peripheral and lymphoid tissues was demonstrated at greater than 200 days after transplant. To investigate the functional significance of this observation, heart donors, and donor bone marrow were irradiated before transplantation in CTLA4-Ig-treated recipients. A reduction in allograft survival was associated with irradiation of both the donor heart and the bone marrow. These results suggest that there may be a donor-derived radiosensitive element that enhances allograft survival in this model. Reverse transcriptase polymerase chain reaction analysis of allografts of tolerant and control animals at days 5, 8, and 12 after transplantation failed to demonstrate a dramatic difference in the expression of interleukin (IL)-2, IL-4, IL-10, and interferon-gamma message. Cytotoxicity effector transcripts were largely intact in CTLA4-Ig + bone marrow-treated recipients as they showed no decrease in intragraft granzyme, perforin, Fas, or Fas ligand transcripts during thr first 8 days after transplant. These results imply that complex mechanisms may be important for the induction and maintenance of transplantation tolerance in the CTLA4-Ig plus bone marrow murine cardiac allograft model.
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PMID:CTLA4-Ig plus bone marrow induces long-term allograft survival and donor specific unresponsiveness in the murine model. Evidence for hematopoietic chimerism. 862 6

We report the sequence of a 23,002 bp fragment located on the right arm of Saccharomyces cerevisiae chromosome VII. Analysis of this region revealed 14 complete open reading frames (ORFs) wit more than 300 base pairs. Six of them correspond to previously known genes. G7164 is the QCR9 gene coding for subunit 9 of the cytochrome c reductase; G7168 is UBR1, encoding an ubiquitin protein ligase; G7522 is the TYS1 gene, which encodes for the tyrosyl tRNA synthetase; G7526 is TFG1, the gene coding for the RNA polymerase transcription initiation factor TFIIF (factor G); G7538 is the gene HGH1 which encodes a protein related to the mammalian HMG1 and HMG2 proteins. G7542 is the BUB1 gene which encodes a ser/thr protein kinase involved in spindle assembly during the cell cycle. One of the ORFs, G7553, shares significant homologies with the gene UTR2 from S. cerevisiae. None of the seven remaining ORFs shows similarity to any of the sequences within the public databases. Three ORFs are internal ORFs of the above-described known genes, and two small ORFs are completely contained in larger ORFs on the complementary strand, and therefore probably do not correspond to real genes. This region also contains three genes specifying tRNAs for Leu, Lys and Trp, and several LTR elements.
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PMID:DNA sequence analysis of a 23,002 bp DNA fragment of the right arm of Saccharomyces cerevisiae chromosome VII. 913 39


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