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)

1. DNA-dependent RNA polymerases A and B were solubilized from rat liver nuclei at different intervals after partial hepatectomy, and chromatographed on DEAE-Sephadex A-25. Activity of the solubilized RNA polymerases remained unchanged till 6 h after hepatectomy, then started to increase reaching a maximum (350% and 150% of control for the A and B enzyme, respectively) at the 18th hour of regeneration, and was still high at the 36th hour of regeneration. 2. RNA polymerases A and B were extracted and extensively purified from the nuclei of normal and regenerating rat liver. No marked differences in the specific activities between the analogous purified enzymes from normal and regenerating liver were observed, thus the increase in RNA polymerase activities (especially marked in the case of enzyme A) observed after partial hepatectomy is probably due to a real increase in the quantities of enzymes. 3. Concentration of RNA polymerase A in hepatocyte increases from 1.3 x 10(4) (normal liver) to 7.5 x 10(4) (18 h after hepatectomy) molecules per haploid genome. The concentration of polymerase B increases from 3.4 x 10(4) to 5.5 x 10(4) molecules per haploid genome, respectively.
Acta Biochim Pol 1978
PMID:Changes in cellular concentration of DNA-dependent RNA polymerases A and B during regeneration of rat liver. 75 2

1. The RNA polymerase I was practically absent in the resting embryos and appeared several hours after the beginning of imbibition, whereas the level of polymerase II was high in the resting embryos and did not increase significantly during the imbibition phase. 2. Incorporation in vivo of [14C]valine into polymerase I and II indicated that the synthesis of RNA polymerase I is initiated in germinating embryos much earlier than that of RNA polymerase II. 3. It is suggested that RNA polymerase II is stored in resting wheat embryos to support mRNA synthesis at the onset of germination, whereas the RNA polymerase I activity appears at a further stage of germination.
Acta Biochim Pol 1976
PMID:RNA polymerases I and II in germinating wheat embryo. 97 38

In HeLa cells, RNA polymerase I (Pol I)-mediated transcription is severely inhibited soon after infection with poliovirus. We have developed a gel retardation assay to analyze DNA-protein complexes formed at the Pol I promoter. We show here that two complexes (A and C) formed by nuclear extracts from uninfected cells disappear after infection of cells with poliovirus. In contrast, a new, rapidly migrating complex (D) is formed in virus-infected cell extract. This change in the mobility of gel-retarded complexes correlates well with the kinetics of inhibition of rRNA transcription in virus-infected cells. Incubation of nuclear extracts from mock-infected cells with bacterially expressed, purified poliovirus protease 3C results in the disappearance of complexes A and C with concomitant generation of complex D. A partially purified transcription factor fraction derived from uninfected cells that contains complex A is able to restore Pol I transcription when added to virus-infected cell extracts, suggesting that this complex plays an important role in Pol I transcription. These results suggest that poliovirus proteinase 3C may have an important role in the shutoff of Pol I transcription in cells infected with poliovirus.
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PMID:Infection of HeLa cells with poliovirus results in modification of a complex that binds to the rRNA promoter. 131 18

The genomic hypervariation of human immunodeficiency virus 1 (HIV-1) could result from misincorporations by the viral reverse transcriptase. We developed an assay for reverse transcriptase fidelity during RNA-dependent as well as DNA-dependent DNA polymerization in vitro. A lacZ alpha RNA fragment transcribed by T3 RNA polymerase was used to mimic first-strand reverse transcription. The corresponding DNA template was used to examine errors by reverse transcriptase during second-strand DNA synthesis. With both templates, the mutations introduced by reverse transcriptase were identified by their mutant phenotypes in an M13 lacZ alpha-complementation assay. We found that the reverse transcriptase from human immunodeficiency virus 1 (HIV-1 RT) was less accurate than the reverse transcriptase from Moloney murine leukemia virus (MLV RT) or the Klenow fragment of Escherichia coli DNA polymerase I (Pol I) on either RNA or DNA templates. The frequency of misincorporation by HIV-1 RT was 1 in 6900 nucleotides polymerized on the RNA template and 1 in 5900 on the DNA template. The error rates of MLV RT and Pol I on the RNA template were less than 1 in 28,000 and 37,000, respectively. The most frequent mutations produced by HIV-1 RT copying the RNA template were C----T transitions and G----T transversions resulting from misincorporation of dAMP.
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PMID:Fidelity of HIV-1 reverse transcriptase copying RNA in vitro. 137 Sep 10

Two human Alu repeats terminating in an oligo(T) run rather than the usual A-rich 3' tail were isolated by library screening. Base sequence comparisons reveal that these unusual Alus are also exceptionally divergent from other Alu family members implying that they are evolutionarily old. Unlike other members of the family, they are not transcribed in vitro by RNA polymerase III (Pol III) suggesting a partial explanation for how Alu source genes might become inactive with age.
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PMID:Unusual sequences of two old, inactive human Alu repeats. 142 Mar 11

We have developed a novel system to study transcription by yeast RNA polymerase I (Pol I) of mutated rDNA units within the chromosomal context. For this, complete rDNA units carrying specific oligonucleotide tags in both the 17S and 26S rRNA genes were integrated into the chromosomal rDNA locus. Using this novel system, we analysed the action of the rDNA enhancer in stimulating transcription within the chromosomal context. We found that the enhancer acts as a stimulatory element in both directions, mainly on its two most proximal rRNA operons. Deletion of the sequences between the enhancer and the Pol I promoter in the tagged, integrated unit indicated that this part of the intergenic spacer contains no other transcriptional regulatory elements for Pol I. We also applied the system to study the function of the rDNA binding protein RBP1/REB1. For this purpose, we analysed tagged units in which either one or both of the binding sites for this protein have been inactivated. We found that mutations of both binding sites strongly diminish the transcription of the adjacent operon. The protein is hypothesized to play a crucial role in keeping the chromosomal rDNA units in an optimal spatial configuration by anchoring consecutive enhancers and promoters to the nucle(ol)ar matrix.
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PMID:A system to study transcription by yeast RNA polymerase I within the chromosomal context: functional analysis of the ribosomal DNA enhancer and the RBP1/REB1 binding sites. 142 96

Double-stranded RNA viruses have an RNA-dependent RNA polymerase activity associated with the viral particles which is indispensable for their replication cycle. Using the yeast L-A double-stranded RNA virus we have investigated the mechanism by which the virus encapsidates its genomic RNA and RNA polymerase. The L-A gag gene encodes the principal viral coat protein and the overlapping pol gene is expressed as a gag-pol fusion protein which is formed by a -1 ribosomal frameshift. Here we show that Gag alone is sufficient for virus particle formation, but that it fails to package the viral single-stranded RNA genome. Encapsidation of the viral RNA requires only a part of the Pol region (the N-terminal quarter), which is presumably distinct from the RNA polymerase domain. Given that the Pol region has single-stranded RNA-binding activity, these results are consistent with our L-A virus encapsidation model: the Pol region of the fusion protein binds specifically to the viral genome (+) strand, and the N-terminal gag-encoded region primes polymerization of Gag to form the capsid, thus ensuring the packaging of both the viral genome and the RNA polymerase.
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PMID:Pol of gag-pol fusion protein required for encapsidation of viral RNA of yeast L-A virus. 143 38

The SRP1-1 mutation is an allele-specific dominant suppressor of temperature-sensitive mutations in the zinc-binding domain of the A190 subunit of Saccharomyces cerevisiae RNA polymerase I (Pol I). We found that it also suppresses temperature-sensitive mutations in the zinc-binding domain of the Pol I A135 subunit. This domain had been suggested to be in physical proximity to the A190 zinc-binding domain. We have cloned the SRP1 gene and determined its nucleotide sequence. The gene encodes a protein of 542 amino acids consisting of three domains: the central domain, which is composed of eight (degenerate) 42-amino-acid contiguous tandem repeats, and the surrounding N-terminal and C-terminal domains, both of which contain clusters of acidic and basic amino acids and are very hydrophilic. The mutational alteration (P219Q) responsible for the suppression was found to be in the central domain. Using antibody against the SRP1 protein, we have found that SRP1 is mainly localized at the periphery of the nucleus, apparently more concentrated in certain regions, as suggested by a punctate pattern in immunofluorescence microscopy. We suggest that SRP1 is a component of a larger macromolecular complex associated with the nuclear envelope and interacts with Pol I either directly or indirectly through other components in the structure containing SRP1.
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PMID:Cloning and characterization of SRP1, a suppressor of temperature-sensitive RNA polymerase I mutations, in Saccharomyces cerevisiae. 144 93

A polyacrylamide gel assay is used to measure the kinetics of adding a single deoxyribonucleotide onto either a correctly matched or mismatched primer 3' terminus (on M13 template) for all possible DNA base pairs and mispairs using Drosophila melanogaster DNA polymerase alpha (Pol alpha) and avian myeloblastosis virus reverse transcriptase. The reverse transcriptase catalyzes chain extension from transition mispairs (Pur.Pyr and Pyr.Pur, where Pur is purine and Pyr is pyrimidine) more efficiently than polymerase alpha. Reverse transcriptase extends G(primer).T almost 20% as efficiently as it extends A.T, while Pol alpha's G.T extension efficiency is less than 1%. For transversion mispairs (Pur.Pur and Pyr.Pyr), reverse transcriptase extends C.T and T.T with greater efficiency than polymerase alpha, while polymerase alpha is more efficient at extending A.G and G.G mispairs. Reverse transcriptase and polymerase alpha extend the G.G mispair at an efficiency of only 10(-6) and 10(-5), respectively, compared with G.C extension. The extension data for the two polymerases are compared with previously reported nucleotide misinsertion data for the same enzymes (Mendelman, L. V., Boosalis, M. S., Petruska, J., and Goodman, M. F. (1989) J. Biol. Chem. 264, 14415-14423). While the results obtained with reverse transcriptase and Pol alpha differ in detail, some general rules are indicated: (a) Pur.Pyr and Pyr.Pur mispairs, especially G.T and T.G, are easy to insert and even easier to extend; (b) Pyr.Pyr mispairs, especially C.C, are difficult to insert and slightly easier to extend; (c) Pur.Pur mispairs, notably G.G, are harder to extend than to insert. The comparison also shows that reverse transcriptase extends almost all mismatches more efficiently than it forms them, G.G being the only mismatch having a significantly lower efficiency of extension than insertion. Polymerase alpha inserts A.A mismatches most efficiently, but extends them inefficiently, thereby reducing the probability that such transversion mutations will occur in vivo. We show theoretically that when mispaired primers compete with properly matched primers for extension by polymerase, the relative velocities of extension depend on the concentration of the next correct dNTP substrate. The extension velocities depart from Michaelis-Menten kinetics by exhibiting positive cooperativity with respect to substrate concentration.
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PMID:Base mispair extension kinetics. Comparison of DNA polymerase alpha and reverse transcriptase. 168 52

Twelve to twenty percent of newly synthesized poly(A) + RNA is transcribed by RNA polymerase III in Ehrlich ascites carcinoma and P3O1 plasmocytoma mouse tumors. Most of this RNA designated as pol IIIpoly(A) + RNA has a size of 160 to 800 nucleotides with a maximum of distribution of ca. 300 nucleotides. Pol IIIpoly(A) + RNA fraction consists of two major classes of molecules corresponding to previously described B1 RNA and B2 RNA with the ratio of 1:4 to 2:3. All B2 RNAs present in poly(A) + fraction contain a long poly(A) segments at the 3' ends. Thus, RNA polymerase III transcripts can be polyadenylated. Several transcripts that hybridize with B2 probe were also observed in poly(A)- RNA. The major components consist of 180, 160, 120 and 95 nucleotides. The 180-nucleotide B2 RNA seems to be a primary transcript from B2 repeat. We suggest that other B2 RNAs are transcribed from truncated copies of B2 element.
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PMID:The most abundant nascent poly(A) + RNAs are transcribed by RNA polymerase III in murine tumor cells. 169 65


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