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)

The transcriptional activity of the topA gene which codes for topoisomerase I was examined. An in vitro assay determined that the P1 promoter was dependent on the sigma 32 subunit of RNA polymerase. The transcriptional activity of the four topA promoters was examined by nuclease S1 mapping of the transcripts during a heat shock. This sigma 32-dependent promoter was shown to function as a heat shock promoter, although topoisomerase I is not a heat shock protein. A possible method of compensation of transcription activity by the other promoters to maintain the level of topoisomerase I during heat shock is proposed.
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PMID:Identification of a heat shock promoter in the topA gene of Escherichia coli. 217 62

The enzymatic replication of plasmids containing the unique (245 base pair) origin of the Escherichia coli chromosome (oriC) can be initiated with any of three enzyme priming systems: primase alone, RNA polymerase alone, or both combined (Ogawa, T., Baker, T. A., van der Ende, A. & Kornberg, A. (1985) Proc. Natl. Acad. Sci. USA 82, 3562-3566). At certain levels of auxiliary proteins (topoisomerase I, protein HU, and RNase H), the solo primase system is efficient and responsible for priming synthesis of all DNA strands. Replication of oriC plasmids is here separated into four stages: (i) formation of an isolable, prepriming complex requiring oriC, dnaA protein, dnaB protein, dnaC protein, gyrase, single-strand binding protein, and ATP; (ii) formation of a primed template by primase; (iii) rapid, semiconservative replication by DNA polymerase III holoenzyme; and (iv) conversion of nearly completed daughter molecules to larger DNA forms. Optimal initiation of the leading strand of DNA synthesis, over a range of levels of auxiliary proteins, appears to depend on transcriptional activation of the oriC region by RNA polymerase prior to priming by primase.
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PMID:Initiation of enzymatic replication at the origin of the Escherichia coli chromosome: primase as the sole priming enzyme. 240 71

Yeast strains with mutations in the genes for DNA topoisomerases I and II have been identified previously. The topoisomerase II mutants (top2) are conditional-lethal, temperature-sensitive mutants defective in the termination of DNA replication and the segregation of daughter chromosomes. The topoisomerase I mutants (top1), including strains with null mutations, are viable and exhibit no obvious growth defects, demonstrating that DNA topoisomerase I is not essential for viability in yeast. In contrast to the single mutants, top1 top2 double mutants grow poorly at the permissive temperature and stop DNA and ribosomal RNA synthesis at the restrictive temperature. Transfer RNA synthesis remains relatively normal. The rate of polyA+ RNA synthesis is down about 3-fold in the double mutant at the non-permissive temperature but the synthesis of three specific RNA polymerase II transcripts is unaffected. The results suggest that DNA replication and at least ribosomal RNA synthesis require an active topoisomerase, presumably to act as a swivel to relieve torsional stress, and that either topoisomerase can perform the required function (except for termination of DNA replication where topoisomerase II is required).
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PMID:DNA topoisomerase activity is required as a swivel for DNA replication and for ribosomal RNA transcription. 244 27

Purified anti-topoisomerase I immunoglobulin G (IgG) was microinjected into nuclei of Chironomus tentans salivary gland cells, and the effect on DNA transcription was investigated. Synthesis of nucleolar preribosomal 38S RNA by RNA polymerase I and of chromosomal Balbiani ring RNA by RNA polymerase II was inhibited by about 80%. The inhibitory action of anti-topoisomerase I IgG could be reversed by the addition of exogenous topoisomerase I. Anti-topoisomerase I IgG had less effect on RNA polymerase II-promoted activity of other less efficiently transcribing heterogeneous nuclear RNA genes. The pattern of inhibition of growing nascent Balbiani ring chains indicated that the transcriptional process was interrupted at the level of chain elongation. The highly decondensed state of active Balbiani ring chromatin, however, remained unaffected after injection of topoisomerase I antibodies. These data are consistent with the interpretation that topoisomerase I is an essential component in the transcriptional process but not in the maintenance of the decondensed state of active chromatin.
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PMID:Microinjection of anti-topoisomerase I immunoglobulin G into nuclei of Chironomus tentans salivary gland cells leads to blockage of transcription elongation. 244 4

Monoclonal anti-Sm antibody, a specificity directed against a constituent of nuclear ribonucleoprotein and considered to be a marker for systemic lupus erythematosus (SLE), was tested for its ability to react with four other rheumatic disease antigens of known enzymatic activity. No binding of the antibody was observed in radioimmunoassays with immobilized protein kinase NII, poly(A) polymerase, or topoisomerase I. In contrast, anti-Sm antibody did react with RNA polymerase I. Under conditions of antibody excess, anti-Sm was determined to bind RNA polymerase I on an equimolar basis, indicating that the polymerase possesses a single epitope recognized by the anti-Sm antibody. Addition of the anti-Sm antibody to in vitro transcription reactions resulted in inhibition of RNA polymerase I activity but had no effect on the reaction catalyzed by RNA polymerase II. When the subunits of RNA polymerase I were separated by polyacrylamide gel electrophoresis under denaturing conditions and incorporated individually into the radioimmunoassay, anti-Sm antibody bound only to the sixth polymerase polypeptide (Mr, 21,000). These data establish an immunological relationship between two important rheumatic disease antigens and help explain the apparent diversity of the autoimmune response in murine and human SLE.
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PMID:Monoclonal antibody against the lupus antigen Sm cross-reacts with RNA polymerase I. 249 8

A specific cosedimentation of proteins and their complexes with DNA at low temperature (M-band technique) has been demonstrated. Model experiments with reconstituted SV40 DNA-topoisomerase I and SV40 DNA-E. coli RNA polymerase complexes demonstrated the potential and capacities of the method. It allows fractionation of DNA-protein complexes from naked DNA and has greater range, higher reproducibility and lower background values than similar methods.
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PMID:[Coprecipitation of proteins and DNA-protein complexes with magnesium sarcolysate: research on an association of topoisomerase I and RNA polymerase with DNA]. 254 Nov 88

A cloned pea chloroplast 16S rRNA gene promoter has been characterized in detail by use of a homologous in vitro transcription system that contains a highly purified chloroplast RNA polymerase. The in vivo and in vitro 16S rRNA transcriptional start site has been identified to be a T on the plus strand, 158 bases upstream of the mature 5' end of the gene. BAL 31 deletions of the 16S rRNA leader region demonstrated that the bases between -66 to +30 relative to the transcriptional start site (+1) are necessary for specific 16S transcription. Disruption of canonical TTGACA or TATAAT elements within this region caused complete transcriptional inactivation and prevented protein binding. The topological requirement for 16S transcription was examined by using a construct that synthesized a transcript from the 16S promoter and released it from a pea plastid putative terminator sequence. This minigene was relaxed in vitro with a topoisomerase I from pea chloroplast. It was shown that the 16S promoter was most active when the minigene plasmid was supercoiled.
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PMID:In vitro analysis of the pea chloroplast 16S rRNA gene promoter. 258 29

In Drosophila melanogaster the five histone genes are within a 5-kilobase region which is repeated 100 times at a single chromosomal site. These 5-kilobase repeats are of two distinct classes, short and long, that differ by approximately 200 base pairs of DNA in the spacer region between the H1 and H3 genes. Since the mRNA-homologous regions of the repeats are highly conserved, one cannot examine differential expression of the repeats by classical hybridization methods. In this study, we assessed their transcriptional activity by measuring in vivo the relative amounts of RNA polymerase II that were cross-linked by UV irradiation to the two different histone repeats. The RNA polymerase II density on the long repeat in Schneider line 2 cells was strikingly lower (10-fold) than the density on the short repeat. The magnitude of this difference cannot be accounted for by reduced transcription of only one or two genes of the repeat. The density of topoisomerase I, an indicator of transcriptional activity, was also much higher on the short repeat than on the long repeat of line 2 cells. In contrast, the RNA polymerase II density was slightly higher on the long repeat than on the short repeat in a second cell line, KcH. The major difference between active (KcH) and inactive (S2) long repeats resides in the H1-H3 nontranscribed spacer. This portion of the spacer may contain a component necessary for expression that can act over a moderate distance and affect multiple genes of the repeat.
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PMID:Protein-DNA cross-linking reveals dramatic variation in RNA polymerase II density on different histone repeats of Drosophila melanogaster. 282 28

Treatment of HeLa cells with a DNA topoisomerase I-specific inhibitor, camptothecin, results in rapid cessation of the synthesis of the 45S rRNA precursor. The inhibition of rRNA synthesis is reversible following drug removal and correlates with the presence of camptothecin-trapped topoisomerase I-DNA abortive complexes, which can be detected as topoisomerase I-linked DNA breaks upon lysis with sodium dodecyl sulfate. These breaks were found to be concentrated within the transcribed region of human rRNA genes. No such sites can be detected in the inactive human rRNA genes in mouse-human hybrid cells, suggesting a preferential association of topoisomerase I with actively transcribed genes. The distribution of RNA polymerase molecules along the transcription unit of human rRNA genes in camptothecin-treated HeLa cells, as assayed by nuclear run-on transcription, shows a graded decrease of the RNA polymerase density toward the 3' end of the transcription unit; the density is minimally affected near the 5' start of the transcription unit. These results suggest that DNA topoisomerase I is normally involved in the elongation step of transcription, especially when the transcripts are long, and that camptothecin interferes with this role.
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PMID:Involvement of DNA topoisomerase I in transcription of human ribosomal RNA genes. 282 14

The duplex DNA unwinding ability of seminalplasmin [corrected] from bovine semen was examined by treatment of plasmid-protein complexes with calf thymus topoisomerase I and resolution of the topoisomer distributions by agarose gel electrophoresis. Binding of seminalplasmin [corrected] results in a moderate degree of unwinding of supercoiled plasmid. The elongation of the RNA chain by E. coli RNA polymerase over promoter containing template is not inhibited by seminalplasmin [corrected]. However, the reinitiation of transcription is blocked in such cases indicating that seminalplasmin [corrected] inhibits transcription by binding to the initiation site of RNA polymerase.
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PMID:Bovine seminalplasmin [corrected] is a DNA unwinding protein. 283 34


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