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)

U RNAs are highly abundant small nuclear RNAs involved in the processing of messenger RNA. Most U RNA genes are thought to be transcribed by RNA polymerase II (pol II). However, evidence has recently been presented that U6 RNA genes are transcribed by RNA polymerase III (pol III). In the light of these results it was surprising to find that the 5' flanking region of a mouse U6 RNA gene includes a perfect copy of the octamer sequence motif, ATTTGCAT, found in many RNA polymerase II transcription enhancer elements. In the present study we show that deletion of mouse U6 gene sequences upstream of nucleotide position -217, including the octanucleotide motif, reduces U6 transcription by 90% when assayed in Xenopus laevis oocytes, suggesting the presence of a distant control element. DNase I footprinting of the 5' flanking region of the U6 gene shows protection of the octanucleotide sequence. Moreover, the 5' flanking sequence from -217 to -315 can replace the enhancer of a human U2 RNA gene. We therefore conclude that although U6 RNA genes appear to be transcribed by pol III, they are preceeded by an enhancer-like element which can functionally substitute for the enhancer of a pol II-transcribed U RNA gene.
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PMID:A distant enhancer element is required for polymerase III transcription of a U6 RNA gene. 329 7

The human ribosomal RNA promoter contains two distinct control elements (UCE and core) both of which are recognized by the sequence-specific DNA binding protein UBF1, which has now been purified to apparent homogeneity. The purified factor activates RNA polymerase I (RNA pol I) transcription through direct interactions with either control element. A second RNA pol I transcription factor, designated SL1, participates in the promoter recognition process and is required to reconstitute transcription in vitro. Although SL1 alone has no sequence-specific DNA binding activity, deoxyribonuclease I footprinting experiments reveal that a cooperative interaction between UBF1 and SL1 leads to the formation of a new protein-DNA complex at the UCE and core elements. In vitro transcription experiments indicate that formation of the UBF1-SL1 complex is vital for transcriptional activation by UBF1. Thus, protein-protein interactions between UBF1 and SL1 are required for targeting of SL1 to cis-control sequences of the promoter.
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PMID:Functional cooperativity between transcription factors UBF1 and SL1 mediates human ribosomal RNA synthesis. 341 83

We have identified a novel RNA polymerase I (pol I) transcription initiation site within the 'non-transcribed' spacer of mouse rDNA. This spacer promoter is located about 2 kb upstream of the 45S pre-rRNA promoter and directs specific transcription initiations both in a cell-free system using truncated templates and in vivo after transfection into mouse cells. The spacer promoter contains an 11 out of 16 bases match to the core element of the major ribosomal gene promoter and is oriented in the same direction. It exerts a significantly lower transcriptional activity as compared to the 45S pre-rRNA promoter. The elongation of transcripts initiated at the spacer promoter is stopped at a termination signal located 170 bp upstream of the pre-rRNA start site. Since it has been previously shown that, in addition to its terminator function, the same sequence motif acts as an upstream element of the adjacent gene promoter, the function of the spacer promoter may be to capture free pol I molecules and drive them to the gene promoter in order to achieve the high level of transcription characteristic of eukaryotic rRNA genes.
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PMID:A novel promoter in the mouse rDNA spacer is active in vivo and in vitro. 342 63

The RNA polymerase III-dependent transcription of B2 repeated sequences has been monitored during the transition from the quiescent to proliferative state in cultured rodent cells and after polyomavirus-induced transformation. The level of RNAs containing B2 sequences was found to be higher in both the proliferative state of normal cells and in polyomavirus-transformed cells. In both systems, nuclear run-off transcription assays indicated that high levels of B2 RNAs are due to an enhanced transcription rate. These results suggest the presence of a B2-specific RNA pol III transcription factor(s) whose activity is sensitive to cell cycle progression and oncogenic transformation.
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PMID:The transcription of B2 repeated sequences is regulated during the transition from quiescent to proliferative state in cultured rodent cells. 360 98

Nuclear extracts from adenovirus-infected HeLa cells harvested early in infection demonstrated a markedly increased capacity for transcription by RNA polymerase III of exogenous VA RNA genes, as well as cloned tRNA and 5S RNA genes. In contrast, no enhanced transcription was observed in extracts from cells infected with an E1A deletion mutant. Moreover, cells co-transfected with the VA- and E1A-containing plasmids showed markedly higher levels of VA RNA synthesis than did cells transfected with the VA-containing plasmid alone. Although analysis of high ionic strength extracts revealed that the enhancement of pol III transcription persists late in infection, moderate ionic strength extracts indicated that transcription factor IIIC becomes limiting. Chromatographic fractionation and complementation analysis of extracts from mock- and virus-infected cells indicated that the factor(s) responsible for the enhanced activity was localized entirely in the fraction containing transcription factor IIIC.
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PMID:Enhancement of RNA polymerase III transcription by the E1A gene product of adenovirus. 400 53

The effect of the antitumor antibiotic illudin S on bacterial macromolecular synthesis was investigated. Illudin S was found to be inhibitory to in vivo deoxyribonucleic acid (DNA) synthesis from thymidine. Ribonucleic acid (RNA) synthesis was inhibited only at a concentration of illudin S 10 times that which inhibited DNA synthesis. The rate of protein synthesis remained the same except for a brief initial inhibition. When thymidine triphosphate was used for in vitro DNA synthesis, inhibition by illudin S did not occur, as tested with partially purified DNA polymerase II from Escherichia coli pol A(1) (-), with E. coli DNA-dependent RNA polymerase, with E. coli pol A(1) (-) spheroplasts, and with frozen and thawed Bacillus subtilis cells. A protein fraction isolated from B. subtilis capable of forming thymidine mono-, di-, and triphosphates from thymidine was not inhibited by illudin S. Furthermore, (14)C-illudin S taken up by B. subtilis cells was reisolated unchanged, making an intracellular activation of illudin S unlikely. Therefore, an attractive hypothesis is that illudin S inhibits DNA synthesis from thymidine which does not proceed through deoxyribonucleoside triphosphates, the generally accepted substrates for DNA synthesis.
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PMID:Mode of action illudin S. 420 86

varphiX174 and M13 (fd) single-stranded circular DNAs are converted to their replicative forms by extracts of E. coli pol A1 cells. We find that the varphiX174 DNA-dependent reaction requires Mg(++), ATP, and all four deoxynucleoside triphosphates, but not CTP, UTP, or GTP. This reaction also involves the products of the dnaC, dnaD, dnaE (DNA polymerase III), and dnaG genes, but not that of dnaF (ribonucleotide reductase). The in vitro conversion of fd single-stranded DNA to the replicative form requires all four ribonucleoside triphosphates, Mg(++), and all four deoxynucleoside triphosphates. The reaction involves the product of gene dnaE but not those of genes dnaC, dnaD, dnaF, or dnaG. The reaction with fd DNA is inhibited by rifampicin or antibody to RNA polymerase, while the reaction with varphiX174 DNA is not affected by either. With the varphiX174 DNA-dependent reaction, activities have been detected that specifically complement extracts of dnaA, dnaB, dnaC, dnaD, or dnaG mutants.
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PMID:Conversion of phiX174 and fd single-stranded DNA to replicative forms in extracts of Escherichia coli. 456 9

Reverse transcriptase from avian retrovirus has a physically associated DNA endonuclease with novel substrate and cofactor requirements. A similar endonuclease activity copurifies with pp32, a protein from viral cores that has been identified with the non-alpha region of the beta subunit of reverse transcriptase. Several temperature-sensitive mutants of avian retrovirus with thermolabile DNA polymerase were tested for thermal sensitivity of their DNA endonuclease activity. Two pol mutants of Rous sarcoma virus, ts335 and ts337, had thermolabile DNA endonuclease; a temperature-resistant revertant of ts335 had a heat-stable DNA endonuclease. DNA endonuclease is therefore a product of the pol gene and an integral part of the reverse transcriptase. A second class of pol mutants, typified by ts568 and ts553, had thermolabile DNA polymerase, but heat-stable DNA endonuclease.
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PMID:Virus-coded DNA endonuclease from avian retrovirus. 616 35

Cloned DNA from the EcoRI J fragment of EBV has been used as template for in vitro transcription experiments using cell-free extracts prepared from HeLa or KB cells. Two EBV specific RNAs each about 175 bases in length were synthesised and nuclease 51 mapping experiments determined that these in vitro products corresponded precisely to the in vivo species obtained from Raji cells. These two RNA molecules are transcribed by RNA polymerase III and in common with other pol III-synthesised RNAs the coding sequences contain intragenic control regions. The relative abundance of the two RNAs synthesised in vitro differs from that observed in vivo.
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PMID:In vitro transcription of two Epstein-Barr virus specified small RNA molecules. 628

A temperature-sensitive coordinate mutant tsLA83 of Prague (PR-B) strain of Rous sarcoma virus at the nonpermissive temperature (41 degrees) produces noninfectious virus particles (NI-LA83) which contained only 3% of the reverse-transcriptase activity present in infectious virions. Analyses of [35S]methionine-labeled NI-LA83 showed the presence of all of the viral proteins except reverse transcriptase. Pulse-chase analyses of the virus-specified proteins in cells infected with LA83 or PR-B showed that the gag and glycoprotein precursors, Pr76gag and gPr95env, respectively, were processed at both 35 and 41 degrees. The reverse-transcriptase precursor, Pr180gag-pol, however, was not processed in LA83-infected cells at 41 degrees. In contrast, cells infected with LA83 or PR-B at 35 degrees as well as with PR-B at 41 degrees showed normal cleavage of Pr180gag-pol. A shiftdown of LA83-infected cells at 41 degrees to the permissive temperature 35 degrees resulted in the normal processing of Pr180gag-pol and production of infectious virus containing reverse transcriptase. Electron microscopic analysis showed that at 41 degrees cells infected with LA83 showed a large number of budding structures but fewer released particles. A shiftdown from 41 to 35 degrees resulted in an increase of virus particles with a concomitant decrease in budding structures suggesting that the processing of reverse-transcriptase precursor is related to virion assembly.
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PMID:Impaired cleavage of the joint gag-pol polyprotein precursor and virion assembly in a temperature-sensitive mutant of Rous sarcoma virus. 633 Sep 81


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