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)

Transcription was determined in liver chromatin from rats fed for 6 days, an optimal (20%) or suboptimal (3%) amount of high-quality protein. Transcription by Escherichia coli RNA polymerase (EC 2.7.7.6) was lower after prolonged incubation with chromatin from rats fed 3% as compared with 20% protein. Differences were detected in the transcripts of the two types of chromatin after analysis by sucrose density gradient centrifugation. But no measurable differences were found in the melting profiles at low ionic strength of the two chromatin preparations. Transcription per milligram chromatin DNA was 25-fold higher using E. coli RNA polymerase instead of rat liver RNA polymerase II. The use of UTP as radioactive precursor in the absence of ATP, GTP and CTP resulted in a low labelling of RNA. One [lambda32P]UTP nucleotide was incorporated/8 UMP nucleotides. The product obtained was sensitive to ribonuclease treatment. In the presence of ATP, GTP and CTP [lambda-32P]UTP nucleotide incorporation was reduced and that of UMP nucleotide was increased giving a ratio of 1:188.
...
PMID:Transcription of rat liver chromatin by Escherichia coli RNA polymerase: template properties after protein restriction. 36 67

The rate of initiation of RNA synthesis catalysed by yeast RNA polymerase A on native calf thymus DNA decayed exponentially with a half-life of about 4.3 min. The rate constant for initiation was unaffected by preincubating the enzyme with DNA, or by decreasing the concentration of GTP 4-fold. The rate of RNA synthesis was constant for 15--20 min and then decreased. Each enzyme molecule made no more than one RNA molecule. In this situation, initiation, elongation and total RNA synthesis are related by a convolution integral. Solution of the convolution integral revealed that the rate of elongation was apparently biphasic. Analysis of the size of the RNA product showed that this biphasic profile arose because most but not all of the enzyme stopped RNA synthesis soon after initiation.
...
PMID:Convolution analysis of transcription by yeast DNA-dependent ribonucleic acid polymerase A. A mathematical method for studying ribonucleic acid chain elongation. 37 33

An enzyme has been isolated from Escherichia coli strains harboring the I-like plasmid R64drd11, which is capable of initiating DNA synthesis on the circular, single-stranded DNA of phages phi X174, fd, and G4. In the conversion of these templates to duplex forms in vitro, the enzyme can substitute for the functions of E. coli dna B-dnaB-dnaC-dnaG proteins, E. coli RNA polymerase, and E. coli dnaG protein, respectively. The enzyme requires all four ribonucleoside triphosphates for optimal activity, although a combination of ATP, CTP, and GTP can almost completely satisfy the rNTP requirement. The enzyme appears to cooperate specifically with DNA polymerases III because single-stranded DNA-dependent synthesis takes place in extracts deficient in DNA polymerases I and II but not in extracts from a dnaZ mutant. Highly purified enzyme preparations consist mostly of two major polypeptides, Mr 140,000 and 180,000, when analyzed by sodium dodecyl sulfate gel electrophoresis. These polypeptides cosediment with the enzyme activity through a glycerol gradient with a sedimentation coefficient of 3.6 S. DNA priming activity in extracts of E. coli strains harboring the mutant plasmids R64drd11 or ColIdrd1, which are derepressed in functions of conjugational DNA transfer, severalfold higher than the activity from strains carrying the corresponding wild-type plasmid. This correlation suggests that the enzyme may play a role in conjugational DNA synthesis.
...
PMID:A DNA primase specified by I-like plasmids. 38 43

Escherichia coli RNA polymerase loses 55-65% of its catalytic activity on reaction with Nbf-Cl (4-choro-7-nitrobenzofurazan). This partial inactivation was shown to be the result of specific impairment of RNA-chain elongation, since initiation of RNA chains was not altered after treatment with Nbf-Cl. The site of reaction was shown to be a unique thiol on the beta-subunit. This thiol is not accessible to reaction with 5,5'-dithiobis-(2-nitrobenzoic acid). No protection of the enzyme against reaction with Nbf-Cl could be obtained with the inhibitor rifamycin nor with calf thymus DNA, GTP or 1,10-phenanthroline, indicating that the unique thiol is probably not within the active site. The specific impairment of RNA-chain elongation thus appears to be the result of a local conformational change which leaves chain initiation unimpaired. Changes observed in the tryptophan fluorescence spectrum of the enzyme or reaction with Nbf-Cl are consistent with formation of a Meisenheimer complex of the reagent with a nucleophilic group on the enzyme near the reactive thiol. It is proposed that formation of such a complex and a subsequent conformational change renders this thiol unusually susceptible to reaction with Nbf-Cl.
...
PMID:Impairment of the catalytic activity of Escherichia coli ribonucleic acid polymerase by a unique reaction of 4-chloro-7-nitrobenzofurazan. 39 51

The phi29 early mRNA's synthesized in infected Bacillus subtilis were studied by using sedimentation velocity analysis, polyacrylamide gel electrophoresis, and hybridization of phi29 DNA fragments generated by the restriction endonuclease Eco RI. Viral RNAs synthesized in vivo in the resence of chloramphenicol were found to hybridize to Eco RI-A, -C, and -D fragments, but not to Eco RI-B and -E fragments, of the viral genome. Major early mRNA sedimenting as 16S material in neutral sucrose gradients was examined in detail. Radioactive phi29 RNA, purified by sucrose gradient centrifugation, was hybridized to either the Eco RI-A or Eco RI-C DNA fragment. The RNA was eluted from the hybrids and then tested for complementary hybrid formation with Eco RI-A and -C fragments. RNA eluted from the Eco RI-A fragment annealed only to the Eco RI-A fragment and not to the Eco RI-C fragment. Similarly, RNA eluted from the Eco RI-C fragment hybridized to the Eco RI-C and -D fragments. Viral RNAs synthesized in vitro using B. subtilis RNA polymerase hybridized to both Eco RI-A and -C DNA fragments. Furthermore, RNA initiated with [gamma-(32)P]GTP also hybridized to both Eco RI-A and -C fragments. These results indicate that there are at least two efficient promotors for early transcription on the phi29 chromosome. In addition, a low-molecular-weight RNA initiated with [gamma-(32)P]ATP was found to hybridize exclusively with the Eco RI-A fragment. Kinetic studies of phi29 mRNA synthesis during the lytic cycle have shown that viral RNAs hybridizable to the Eco RI-A and -C fragments are synthesized immediately after phage infection. On the other hand, mRNA specific for the Eco RI-B fragment was not synthesized for several minutes after phage infection. Based on the results of the in vivo and in vitro transcription studies, a transcription map of the phi29 chromosome is proposed.
...
PMID:Transcription of the genome of bacteriophage phi 29: isolation and mapping of the major early mRNA synthesized in vivo and in vitro. 40 15

Some properties of unprimed poly(A)-poly(U) synthesis by DNA-dependent RNA polymerase from Caulobacter crescentus were examined. The reaction required ATP and UTP as substrates and manganese as a divalent cation. Rifampicin completely inhibited the reaction at a concentration of 1 micron/ml, and the enzyme catalyzed the polymer synthesis well regardless of the presence of GTP, CTP or both. The chain length of the poly(A)-poly(U) synthesized was about one hundred base pairs, as estimated from a sedimentation velocity and the molar ratio of [3H]AMP to [gamma-32P]ATP incorporated into the poly(A)-poly(U). The reaction was dependent on the square of the enzyme concentration and the enzyme dimers formed complexes with poly(A)-poly(U) during the reaction.
...
PMID:Properties of unprimed poly(A)-poly(U) synthesis by Caulobacter crescentus RNA polymerase. 42 57

When protein biosynthesis is inhibited by either cycloheximide of puromycine, the nucleolar RNA synthesis of Ehrlich ascites tumor cells decreases by approximately 70% within 1 h, while the removal of these protein synthesis inhibitors causes a rapid recovery of nucleolar RNA synthesis, largely within 1 h. A similar pattern of decrease and recovery of endogenous RNA polymerase activity in isolated nucleoli or in nuclei (in the presence of alpha-amanitin) may be demonstrated after addition and removal of these drugs. Analysis of the molecular species of RNA polymerase I on a phosphocellulose column indicates that only the IB form of the enzyme decreases in the nucleoli of drug-treated cells and recovers quickly after resumption of protein synthesis. The finding that the activity of the IB form enzyme remains unchanged in the whole nuclei indicates that during cessation of protein synthesis RNA polymerase IB is either released from the nucleoli into the extranucleolar compartment or becomes so loosely bound to the nucleoli that it is leached out from the nucleoli during their isolation. By using a system of assaying free, nucleolar-template bound and total RNA polymerase I activities, data supporting the above interpretation have been obtained. Namely, in isolated nuclei free enzyme activity increases with a concomitant decrease in bound enzyme activity during protein synthesis inhibition, while the total enzyme activity remains unchanged. In isolated nucleoli, both total and bound enzyme activities decreases on protein synthesis inhibition but recover quickly on its resumption. The putative bound enzyme, fractionated with the aid of actinomycin D, is exclusively IB form, whereas the unbound enzyme consists of both IA and IB forms as previously demonstrated (1). No conversion of IB form polymerase to IA form was noted on prolonged sonication in our system. The levels of ATP and GTP in the cell did not change appreciably either during cessation or resumption of protein synthesis in these cells. The data support the previous conclusion that some short-lived protein(s) is required to maintain the normal level of ribosomal RNA transcription (2) and further suggest that the protein is required to facilitate reinitiation of the transcription by RNA polymerase IB in the nucleolus.
...
PMID:The mechanism of decrease in nucleolar RNA synthesis by protein synthesis inhibition. 42 65

Although cordycepin 5'-triphosphate (3'-dATP), at low concentrations, preferentially inhibits chromatin-associated poly(A) synthesis in isolated nuclei, higher levels of the inhibitor prevent both rRNA (RNA polymerase I activity) and hnRNA (RNA polymerase II activity) synthesis in vitro (Rose, K.M., Bell, L.E. and Jacob, S.T. (1977) Nature 267, 178-180). The present studies demonstrate that this nucleotide can also inhibit tRNA and 5 S RNA synthesis (RNA polymerase III activity). At 50-200 microgram/ml, 3'-dATP inhibits incorporation of [3H]UTP into tRNA and 5 S RNA by approximately 65%, whereas the syntheses of these RNAs were completely blocked when [3H]GTP was used as the substrate. These data suggest the formation of poly(U) in the tRNA and 5 S RNA regions, which is resistant to 3'-dATP. In contrast, another ATP analog, Ara-ATP, which selectively inhibits poly(A) synthesis, does not block tRNA and 5 S RNA synthesis in isolated nuclei. The production of these RNA species in isolated nuclei is also insensitive to Ara-CTP and 2'-dATP. These data suggest that 3'-dATP exerts general inhibitory effects on RNA synthesis and further substantiate the conclusion that Ara-ATP is a selective inhibitor of the polyadenylation reaction in vitro.
...
PMID:Differential effects of cordycepin triphosphate and 9 beta-D-arabinofuranosyladenine triphosphate on tRNA and 5 S RNA synthesis in isolated nuclei. 49 5

Bacteriophage T3-induced RNA polymerase is rapidly inactivated at 42 degrees C. Addition of T3 DNA delays this process for 30 s and reduces the rate with which the enzyme activity is lost indicating that a labile binary complex between T3 DNA and polymerase must have been formed. The ternary complex between T3-specific RNA polymerase, T3 DNA, and nascent RNA chains obtained when the enzyme is incubated with T3 DNA, GTP, ATP, and UTP is stable to heat (42 degrees C) and only slowly inactivated by polyvinyl sulfate. The optimal temperature for the formation of polyanionresistant ternary complexes is 30 degrees C while the elongation of T3 RNA chains proceeds fastest at 38 degrees C.
...
PMID:Effect of temperature on the transcription by bacteriophage T3-induced RNA polymerase. 54 12

Initiation of adenovirus transcription was analyzed by incubation of isolated nuclei from virus infected cells in the presence of beta-32P GTP or beta-32P ATP. Nucleotide analysis of RNA from nuclei incubated with beta-32P GTP shows that the label is incorporated exclusively into pppGp and ppGp. Under similar incubation conditions, the label from beta-32P ATP was incorporated primarily into the 5' phosphate of 5', 3' mononucleoside diphosphates, but label was also detected in pppAp, pppGp and in the 3' nucleoside monophosphates. Analysis of RNA, synthesized in the presence of different concentrations of alpha-amanitin, shows that only RNA polymerase III initiates virus specific transcription in isolated nuclei. The virus specific transcripts containing pppAp and pppGp in their 5' termini were identified as the 5.5S and 5.2S viral RNA species by hybridization and finger printing.
...
PMID:Initiation of transcription in nuclei isolated from adenovirus infected cells. 64 9


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

---