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)

Vitellogenin (VTG) synthesis has been described as an ideal system to study the hormonal regulation of gene expression. In Xenopus the molecular aspects of this control have been analyzed; however, in other non-mammalian species such as reptiles, very few studies approaching this level have been undertaken. We report on the induction by estradiol-17 beta of VTG-like proteins in liver explants from adult males and immature male and female lizards (A. pulchellus). A concentration of 10(-7) M was optimum for adult males while a higher concentration (10(-6) M) is required for the immature animals. No differences were observed in the hormonal induction in male and female immature animals, suggesting that there are no sexual distinctions in the liver at this stage. The effect of the hormone in male liver appears to be primarily on mRNA synthesis, since increases in 3H-uridine incorporation in total RNA were prevented by addition of 1 microgram/ml of the RNA polymerase II inhibitor alpha-Amanitin; however, rRNA synthesis was also increased as observed by agarose gel analysis. A 48 hr lag period was required for the detection of the intracellular as well as the secreted VTG-like protein. Electrophoretical analysis of the secretory products revealed the induction of a group of phosphoproteins immunologically related to yolk lipovitellin whose molecular weights range from 116,000 to 200,000.
...
PMID:Vitellogenesis in Anolis pulchellus: induction of VTG-like protein in liver explants from male and immature lizards. 179 22

The miscoding potential of N2,3-ethenoguanine (epsilon G), one of the carcinogen vinyl chloride adducts to DNA bases, has been evaluated in an Escherichia coli DNA-dependent RNA polymerase in vitro system. Epsilon G present in poly(C) templates causes incorporation of cytosine (C), uridine (U) and adenosine (A) under competitive and non-competitive conditions, and in the presence of either Mn2+ and Mg2+ cations, indicating that this modified base still retains the coding properties of unmodified G and can also act as A or U. The formation of hydrogen bonded pairs between different tautomeric forms of epsilon G and C, U and A is proposed. The possible role of epsilon G, along with a role of other vinyl chloride adducts in causing of GC----AT transitions, the most frequent mutation induced by a vinyl chloride metabolite, is discussed.
...
PMID:Miscoding potential of N2,3-ethenoguanine studied in an Escherichia coli DNA-dependent RNA polymerase in vitro system and possible role of this adduct in vinyl chloride-induced mutagenesis. 179 43

We have used a plasmid antitermination test system to examine the response of an Escherichia coli rRNA operon antiterminator to transcription through Rho-dependent and Rho-independent terminator-containing fragments. We also monitored transcription through multiple copies of a terminator to explore the mechanism of rrn antitermination. Four principal observations were made about antitermination and transcriptional terminators. (1) The rrn antiterminator mediated efficient transcription through Rho-dependent terminators. (2) Under the influence of the rrn antiterminator, RNA polymerase transcribed through two and three copies of the Rho-dependent 16 S----terminator with nearly the same efficiency as through one. (3) The antiterminator had less effect on fragments containing Rho-independent terminators; the rpoC t fragment and three fragments derived from the rrnB terminator region stopped antiterminated transcription. Four other Rho-independent terminator fragments were weakly antiterminated in our test system. (4) Surprisingly, the strength of these terminator fragments was not strongly related to properties such as the -delta G or number of trailing uridine residues of their canonical Rho-independent structures, but appears to be related to additional downstream terminators. We have drawn the following conclusions from these experiments. First, that ribosomal antitermination primarily reverses Rho-dependent termination by modifying the RNA polymerase elongation complex. Transcription through a 1700 nucleotide, multiple terminator sequence showed that the antiterminator caused persistent changes in the transcription process. Second, that fragments derived from the Rho-independent rrnB and rpoBC terminator regions can effectively stop antiterminated transcription. Third, that efficient in vivo termination may often involve regions with complex multiple terminators.
...
PMID:Antitermination of characterized transcriptional terminators by the Escherichia coli rrnG leader region. 218 97

Poliovirus RNA polymerase requires a host factor to initiate RNA synthesis in vitro. The host factor was previously purified to near homogeneity from HeLa cells but was not assigned an enzymatic activity. This report describes the purification of a terminal uridylyltransferase that can act as host factor. By all criteria examined it is identical to the factor purified previously. It has the same molecular weight (68,000), chromatographic properties, and cellular localization. We present evidence that terminal uridylyltransferase can add uridine residues to the 3' poly(A) end of virion RNA and that these anneal back to the poly(A) and form a hairpin primer for polymerase.
...
PMID:Purification of a terminal uridylyltransferase that acts as host factor in the in vitro poliovirus replicase reaction. 241 40

We have investigated the mechanism of inhibition of RNA synthesis by methyl mercury (MeHg) in isolated neonatal rat cerebellar cells. Each of the three component steps involved in the incorporation of exogenous [3H]uridine into cellular RNA was examined separately in whole-cell and/or subcellular preparations. Nuclear RNA polymerase activity was measured in preparations containing both free nuclei and whole cells. Incorporation of [3H]UTP into nuclear RNA was found to be unimpaired at concentrations of MeHg that inhibited whole-cell incorporation of [3H]uridine by greater than 75%. Cellular uptake of [3H]uridine was assayed in cerebellar cells treated with KCN to deplete ATP levels and block subsequent phosphorylation reactions of transported uridine. Uptake activity under these conditions was unaffected by MeHg. Measurement of intracellular phosphorylation of [3H]uridine indicated that inhibition of this activity closely paralleled that of RNA synthesis. Quantitation of individual uridine nucleotides by polyethyleneimine-cellulose TLC revealed reduced levels of UTP and UDP whereas levels of UMP were elevated, suggesting that impairment of phosphorylation was not the result of cellular ATP depletion but, more likely, a direct effect on phosphouridine kinase enzymes. This mechanism of MeHg-induced inhibition of RNA synthesis was confirmed by assays of uridine phosphorylation using cell-free extracts in which exogenous ATP was supplied.
...
PMID:Mechanism of apparent transcription inhibition by methyl mercury in cerebellar neurons. 242 3

Subunits of RNA polymerase II that come into contact with nascent RNA transcripts have been determined by photoaffinity labeling. Transcription was carried out in a cell-free extract in the presence of 4-thio-UTP, and utilized the major late promoter of adenovirus-2 DNA. The transcript length was limited by inclusion of the chain terminator 3'-O-methyl-GTP. Transcription complexes were irradiated with near-UV light (lambda greater than 300 nm) to specifically photoactivate 4-thio-uridine. After photocross-linking, radiolabeled proteins were separated by electrophoresis, blotted onto nitrocellulose, and visualized by autoradiography. Specific photoaffinity labeling of enzyme subunits IIo and IIc was observed. In some experiments, radiolabeled IIa was also detected. Based on the level of photoaffinity labeling of subunits IIo and IIa, relative to their concentration in the transcription reaction, the transcriptional activity of RNA polymerase IIO appears to be greater than 10 times that of IIA. RNA attached to subunits IIo and IIc was estimated to be 16-40 nucleotides in length, whereas RNA attached to subunit IIa was approximately 27-40 nucleotides long. Photoaffinity labeling was sensitive to alpha-amanitin, and required DNA containing an RNA polymerase II promoter.
...
PMID:RNA contacts subunits IIo and IIc in HeLa RNA polymerase II transcription complexes. 242 53

We examined the effects of convulsive seizures on in vitro RNA synthesis by cerebral cortex nuclei in El mice. The rate of incorporation of [3H]uridine-5'-triphosphate by intact nuclei during seizures was decreased to 47.4% compared with the rate during the interictal period, but gradually recovered. During the 30-min period after onset of seizures, the rate of RNA synthesis was significantly lower in El mice than in identically stimulated ddY mice. Seizures in El mice had no effect on liver RNA synthesis, suggesting that the alteration of RNA polymerase activity is specific to the brain. Analysis of gel electrophoresis of polyadenylated RNA synthesized in the presence of ammonium sulphate revealed a marked decrease in high-molecular weight RNA species 15 min after seizures in El mice compared with the pattern in nonstimulated ddY mice. This shift from high- to low-molecular weight RNA species was not attributable to RNase activity, but it appeared to be related RNA polymerase.
...
PMID:Alteration of RNA synthesis in vitro in intact cerebral cortex nuclei induced by convulsions in seizure-susceptible El mice. 243 22

To determine whether RNA polymerase pauses during transcription in vivo, we have examined transcripts of the trp operon leader regions of Serratia marcescens and Escherichia coli. Labeled RNAs synthesized in E. coli strains containing plasmids bearing wild-type or mutant trp leader regions of S. marcescens or E. coli were isolated by hybridization and analyzed by polyacrylamide gel electrophoresis. The labeled RNAs synthesized in vivo on the S. marcescens wild-type and deletion mutant plasmids were the same size as the in vitro pause and leader transcripts. Hybridization of the presumed in vivo pause RNAs, and control in vitro pause RNAs, to M13 phage DNA containing a trp leader region deletion followed by treatment with S1 nuclease produced identical protected RNA species, proving that the in vitro and in vivo RNAs were identical. The amount of labeled pause RNAs relative to leader RNAs decreased following a chase with unlabeled uridine. E. coli RNAs identical to the previously characterized in vitro pause and leader transcripts were demonstrated by electrophoretic band position and fingerprint analysis. The finding that transcription pausing occurs in vivo is consistent with the view that transcription pausing and ribosome release of paused transcription complexes are responsible for the coupling of translation with transcription that is crucial to attenuation.
...
PMID:Detection of transcription-pausing in vivo in the trp operon leader region. 243 19

Analysis of puffing patterns in Drosophila melanogaster salivary gland chromosomes indicates the existence of a developmentally specific puff in the 35B region. This puff seems to originate from bands 35B2 or 35B3, where Adh is located, and it is expanded in more than 60% of the nuclei examined. The presence of RNA polymerase II in this puff as well as its ability to incorporate tritiated uridine shows that it corresponds to a transcriptionally active site. RNA blotting and in situ hybridization experiments indicate that Adh is transcribed, although not very actively, in salivary glands during the third larval instar. However, this tissue does not display detectable levels of ADH activity. By contrast, we have found that in midgut polytene chromosomes the 35B region is not visibly puffed in spite of the high levels of Adh transcripts detected. These results seem to suggest that puffing at the 35B region could be mainly promoted by genes closely linked to Adh, possibly with a minor contribution of this gene.
...
PMID:A cytological and molecular analysis of Adh gene expression in Drosophila melanogaster polytene chromosomes. 246 76

3'-Fluoro-3'-deoxy-uridine, -cytidine, -adenosine and -guanosine have been synthesized by glycosylation of the corresponding silylated bases with 1-O-acetyl-2,5-di-O-benzoyl-3-fluoro-3-deoxy-D-ribofuranose in the presence of Friedel-Crafts catalysts and were converted to the 5'-triphosphates, NTP(3'-F). It was shown that NTP(3'-F) are terminators of RNA synthesis catalyzed by DNA-dependent RNA polymerase from E. coli and may thus serve as tools for DNA sequencing.
...
PMID:3'-Fluoro-3'-deoxyribonucleoside 5'-triphosphates: synthesis and use as terminators of RNA biosynthesis. 247 15


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---