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

---

Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We present the primary structure of a chloroplast tRNAArgACG gene of the plant, Pelargonium zonale, and its faithful expression in Xenopus oocyte nuclei. This tRNAArg gene is located 250 bp downstream of a 5S RNA gene within a cloned 5kb long ribosomal DNA segment (Fig. 1). The Pelargonium tRNAArg gene shares 97% and 86% sequence homology with tRNAArgACG genes of Spirodela oligorhiza and Euglena gracilis chloroplasts, respectively, and also extensive homology (70%) with the corresponding gene of E. coli. It lacks an intervening sequence and, like eukaryotic tRNA genes, does not code for the 3' terminal CCA nucleotides. Moreover, the chloroplast tRNAArg gene carries all the sequence elements essential for transcription by vertebrate RNA polymerase III since it is efficiently expressed in Xenopus oocyte nuclei, even in the presence of 1 microgram/ml alpha-amanitin. In Xenopus oocyte nuclei, no transcripts of the chloroplast 5S RNA gene were detected.
...
PMID:A transfer RNAArg gene of Pelargonium chloroplasts, but not a 5S RNA gene, is efficiently transcribed after injection into Xenopus oocyte nuclei. 620 11

The DNA sequence of a cluster of twenty-one tRNA genes distal to a rRNA gene set in B. subtilis was determined. None of the tRNA genes are repeated in the sequence. The only classes of tRNAs that are not represented are those for cysteine, glutamine, tryptophan, and tyrosine. Three of the tRNA genes in this cluster do not have the 3'-CCA sequence encoded in the gene. There is no RNA polymerase terminator sequence in the region between the 5S gene and the first tRNA gene or within the tRNA gene cluster. A terminator sequence was found directly after the last tRNA gene. This rRNA and tRNA gene cluster probably represents one transcriptional unit. However, there may be an RNA polymerase promoter site within this sequence, which raises some interesting questions concerning the regulation of transcription for these tRNA genes.
...
PMID:Sequence analysis of a cluster of twenty-one tRNA genes in Bacillus subtilis. 631 May 12

From a recombinant lambda phage, we have determined a 317-bp sequence containing a mouse tRNAiMet gene. The coding region is precisely homologous to mammalian tRNAiMet if post-transcriptional modifications (including addition of the 3'-terminal CCA) are not considered. The gene does not contain introns and has a typical RNA polymerase III termination site in the 3'-flanking region. It is transcribed by RNA polymerase III in the HeLa cell S-100 system in vitro. Notably, the 5'-flanking region of the mouse tRNAiMet gene shares a "patchwork" pattern of homology with one of the human tRNAiMet genes of Santos and Zasloff [Cell 23 (1981) 699-710]. The 5'-flanking regions of the two genes contain strings of nucleotides, 6 to 32 bp in length, the homology of which is 76-100%. These are separated by short strings of unrelated nucleotides. This is one of the first examples of tRNA genes containing homologous 5'-flanking regions isolated from distantly related mammals. We also report a novel method for constructing deletion mutants of sequences cloned in M13 vectors.
...
PMID:Structure and evolution of mammalian tRNA genes: sequence of a mouse tRNAiMet gene, the 5'-flanking region of which is homologous to a human gene. 656 52

We analyzed the effect of 18 single nucleotide changes on the processing of the transcripts produced by cloned yeast tRNATyr genes after microinjection into the nucleus of living Xenopus oocytes. The processing step most easily blocked by mutation is the early maturation of the 5' and 3' termini of the tRNATyr primary transcript, involving removal of 5'-leader and 3'-trailer sequences and CCA addition. The enzymes seem to recognize the whole tRNA cloverleaf structure since mutations in all regions of the molecule can stop processing. Mutations that affect splicing of the 92-nucleotide precursor (which has mature ends but still contains the intervening sequence, and is the normal substrate for the splicing enzymes), are located in the vicinity of the intervening sequence. Base modification enzymes that add pseudouridine, 1-methyladenosine and 5-methylcytosine appear rather insensitive to changes in secondary and tertiary structure of early transcripts in the 16 mutants examined. These enzymes may recognize only limited regions of the precursor RNA. RNA polymerase III behaves as if able to count the number of Us added before termination; and aberrant termination products in two mutants suggest that the secondary structure of the nascent transcript can be very imortant in eukaryotic transcription termination.
...
PMID:Genetic analysis of the processing of a spliced tRNA. 692 26

A series of C4N hairpin RNAs bearing anticodon nucleotides at the 5' ends and a discriminator base and the sequence CCA at the 3' ends was constructed by an in vitro transcription system using T7 RNA polymerase. These RNAs were aminoacylated specifically with their cognate amino acids by reaction with aminoacyl-adenylates in the presence of a dipeptide, valyl-aspartic acid, suggesting that such hairpin RNAs are able to play the role of the present-day tRNA and that valyl-aspartic acid can perform the function of the present-day aminoacyl-tRNA synthetase as a catalyst in the aminoacylation reaction. These results should provide a useful clue to elucidating the origin of the genetic code.
...
PMID:Specific aminoacylation of C4N hairpin RNAs with the cognate aminoacyl-adenylates in the presence of a dipeptide: origin of the genetic code. 777 94

In eukaryotic cells, RNA polymerase II- and III-transcribed promoters can be inactivated by sequence-specific methylation. For some promoter motifs, the introduction of 5-methyldeoxycytidine (5-mC) residues has been shown to alter specific promoter motif-protein interactions. To what extent does the presence of 5-mC in promoter or regulatory DNA sequences affect the structure of DNA itself. We have investigated changes in DNA bending in three naturally occurring DNA elements, the late E2A promoter of adenovirus type 2 (Ad2) DNA, one of our main model systems, the VAI (virus-associated) RNA gene of Ad2 DNA, and an Alu element associated with the human angiogenin gene. Alterations in electrophoretic mobility of differently permuted promoter segments in non-denaturing polyacrylamide gels have been used as assay system. In the late E2A promoter of Ad2 DNA, a major and possibly some minor DNA bending motifs exist which cause deviations in electrophoretic mobility in comparison to coelectrophoresed marker DNA fragments devoid of DNA bending motifs. DNA elements have been specifically in vitro methylated by the HpaII (5'-CCGG-3'), the FnuDII (5'-CGCG-3'), or the CpG DNA methyltransferase from Spiroplasma species (M-SssI; 5'-CG-3'). Methylation by one of these DNA methyltransferases influences the electrophoretic mobility of the three tested promoter elements very strikingly, though to different extents. It cannot be predicted whether sequence-specific promoter methylation increases or decreases electrophoretic mobility; these changes have to be experimentally determined. Methylation of the E. coli dcm (5'-CCA/TGG-3') sites in some of the DNA constructs does not make a contribution to mobility changes. It is concluded that sequence-specific methylations in promoter or regulatory DNA elements can alter the bending of DNA very markedly. This parameter may contribute significantly to the silencing of promoters, probably via altering spatial relationships among DNA-bound transcription factors.
...
PMID:The topology of the promoter of RNA polymerase II- and III-transcribed genes is modified by the methylation of 5'-CG-3' dinucleotides. 804 19

An in vitro system was established to study the transcription and processing of threonine tRNA using spinach chloroplast enzyme extract. Experiments using a series of 5' deletion mutants demonstrated that the transcription of trnT gene required no 5' upstream promoter elements. Four plasmid DNA templates containing trnT were constructed for tRNA processing assay. The processing reaction was carried out either with exogenously added precursor-tRNAs made by T7 RNA polymerase or with RNAs synthesized by the transcription activity in the same processing enzyme extract. Both assays demonstrated that the 5' and 3' ends of mature tRNA were processed endonucleolytically and the processing of the 5' end preceded the maturation of the 3' end. The activity of nucleotidyl transferase that adds CCA nucleotides to the 3' end of tRNA was also observed. The use of a coupled transcription and processing system provides us with a better insight to the tRNA processing mechanism of the chloroplast.
...
PMID:Transcription and processing of the gene for spinach chloroplast threonine tRNA in a homologous in vitro system. 914 43

Murine gammaherpesvirus 68 (MHV-68) is a virus of wild rodents and is a convenient small animal model for studies of gammaherpesvirus pathogenesis. We have sequenced 6162 bp at the left end of the MHV-68 genome and identified two unique open reading frames (ORFs) (ORF2 and ORF3) and an ORF (ORF1) which displays similarity to poxvirus members of the serpin family. Interspersed with the ORFs is a family of eight novel tRNA-like sequences sharing tRNA-like predicted secondary structures and RNA polymerase III promoter elements. These sequences are expressed to high levels during lytic infection and are processed into mature tRNAs with post-transcriptionally added 3' CCA termini, indicating their recognition as tRNAs by cellular machinery. Acidic Northern analysis of four tRNAs tested has demonstrated that they are not aminoacylated by aminoacyl-tRNA synthetases present in the infected cell. Thus, it is currently unclear what biological function these uncharged viral tRNA-like sequences may fulfil. In situ hybridization analysis has shown that in addition to being expressed within productively infected tissues during acute stages of infection, the tRNA-like sequences are abundantly expressed within splenic germinal centres of latently infected mice. Therefore, the MHV-68 viral tRNAs represent a marker for latent infection and constitute the first report of tRNA-like sequences encoded by a virus of eukaryotes.
...
PMID:Murine gammaherpesvirus 68 encodes tRNA-like sequences which are expressed during latency. 922 45

The universal 3'-terminal CCA sequence of all transfer RNAs (tRNAs) is repaired, and sometimes constructed de novo, by the CCA-adding enzyme [ATP(CTP):tRNA nucleotidyltransferase]. This RNA polymerase has no nucleic acid template, yet faithfully builds the CCA sequence one nucleotide at a time using cytidine triphosphate (CTP) and adenosine triphosphate (ATP) as substrates. All previously characterized CCA-adding enzymes from all three kingdoms are single polypeptides with CCA-adding activity. Here, we demonstrate through biochemical and genetic approaches that CCA addition in Aquifex aeolicus requires collaboration between two related polypeptides, one that adds CC and another that adds A.
...
PMID:Collaboration between CC- and A-adding enzymes to build and repair the 3'-terminal CCA of tRNA in Aquifex aeolicus. 1170 27

Bacteriophage phiKZ is a giant virus that efficiently infects Pseudomonas aeruginosa strains pathogenic to human and, therefore, it is attractive for phage therapy. We present here the complete phiKZ genome sequence and a preliminary analysis of its genome structure. The 280,334 bp genome is a linear, circularly permutated and terminally redundant, A+T-rich double-stranded DNA molecule. The phiKZ DNA has no detectable sequence homology to other viruses and microorganisms, and it does not contain NotI, PstI, SacI, SmaI, XhoI, and XmaIII endonuclease restriction sites. The genome has 306 open reading frames (ORFs) varying in size from 50 to 2237 amino acid residues. According to the orientation of transcription, ORFs are apparently organized into clusters and most have a clockwise direction. The phiKZ genome also encodes six tRNAs specific for Met (AUG), Asn (AAC), Asp (GAC), Leu (TTA), Thr (ACA), and Pro (CCA). A putative promoter sequence containing a TATATTAC block was identified. Most potential stem-loop transcription terminators contain the tetranucleotide UUCG loops. Some genes may be assigned as phage-encoded RNA polymerase subunits. Only 59 phiKZ gene products exhibit similarity to proteins of known function from a diversity of organisms. Most of these conserved gene products, such as dihydrofolate reductase, ribonucleoside diphosphate reductase, thymidylate synthase, thymidylate kinase, and deoxycytidine triphosphate deaminase are involved in nucleotide metabolism. However, no virus-encoded DNA polymerase, DNA replication-associated proteins, or single-stranded DNA-binding protein were found based on amino acid homology, and they may therefore be strongly divergent from known homologous proteins. Fifteen phiKZ gene products show homology to proteins of pathogenic organisms, including Mycobacterium tuberculosis, Haemophilus influenzae, Listeria sp., Rickettsia prowazakeri, and Vibrio cholerae that must be considered before using this phage as a therapeutic agent. The phiKZ coat contains at least 40 polypeptides, and several proteins are cleaved during virus assembly in a way similar to phage T4. Eleven phiKZ-encoded polypeptides are related to proteins of other bacteriphages that infect a variety of hosts. Among these are four gene products that contain a putative intron-encoded endonuclease harboring the H-N-H motif common to many double-stranded DNA phages. These observations provide evidence that phages infecting diverse hosts have had access to a common genetic pool. However, limited homology on the DNA and protein levels indicates that bacteriophage phiKZ represents an evolutionary distinctive branch of the Myoviridae family.
...
PMID:The genome of bacteriophage phiKZ of Pseudomonas aeruginosa. 1191 76


<< Previous 1 2 3 4 Next >>

---