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)

Protein n' of Escherichia coli is required for formation of the prepriming complex in replication of the single-stranded circle of phiX174 DNA. The protein, purified to near homogeneity, possesses ATPase (dATPase) activity in the presence of single-stranded, but not duplex, DNAs. Except for phiX174 DNA, ATPase activity is completely suppressed by coating the DNA with single strand binding protein (SSB). phiX174 DNA possesses a unique sequence with a potential hairpin structure that is recognized as an effector (Shlomai, J., and Kornberg, A. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 799-803). Sequences with secondary structure in SSB-coated M13 DNA which are recognized by RNA polymerase, and in coated G4 DNA by primase, are inert for protein n'. Approximately 30 of the 180 molecules of SSB bound to phiX DNA are destabilized by protein n' in an ATP-dependent reaction. These actions by protein n' may be important in recognizing an origin for forming the prepriming complex that leads to initiation of phiX complementary strand synthesis.
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PMID:A prepriming DNA replication enzyme of Escherichia coli. II. Actions of protein n': a sequence-specific, DNA-dependent ATPase. 610 66

Poly(C) and heparin at low concentrations (1 microgram/ml) prevent the RNA synthesis termination protein rho from functioning during the biosynthesis of RNA from bacteriophage T7 DNA catalyzed by Escherichia coli RNA polymerase. Both of these polyanions inhibit the binding of rho to isolated T7 RNA. Heparin also inhibits rho ATPase when isolated RNA transcripts are used as cofactors. It is concluded that the polyanions inhibit termination by binding to the site on rho that is normally used for the initial interaction with a nascent RNA transcript in the rho-mediated release of RNA. Since one of the inhibitors, poly(C), is itself a potent activator for rho ATPase, it is also concluded that the ATP hydrolysis step that is required for rho termination has to be coupled to an action of rho on the RNA molecule to be released from the transcription complex.
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PMID:Inhibition of the action of Escherichia coli transcription termination protein rho by poly(C) and heparin. 611 50

The effects of pyrophosphate on RNA binding and ATPase activities of Escherichia coli transcription termination factor rho have been studied. Mutant rho-115 protein has a temperature-sensitive RNA-dependent ATPase activity due to the thermolability of binding to RNA [Kent, R.B. & Guterman, S.K. (1981) Fed. Proc. Fed. Am. Soc. Exp. Biol. 40, 1765 (abstr.)]. The presence of either ATP or pyrophosphate at comparable concentrations stabilizes the binary complex of rho and poly(C) at high temperature. ADP at 8-fold greater concentration also stabilizes the mutant rho-RNA binary complex. Pyrophosphate is a noncompetitive inhibitor (Ki = 0.07 mM) of rho poly(C)-dependent ATPase, an activity that is required for rho-mediated termination. These results suggest the existence of a regulatory site on the rho molecule. We suggest that rho NTPase is regulated by RNA polymerase (EC 2.7.7.6) so that during transcription elongation the RNA polymerase competes successfully with rho for substrates and inhibits rho NTPase with product pyrophosphate. Further, RNA polymerase pausing may result in reduced pyrophosphate and increased NTP concentrations, allowing rho NTPase to function.
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PMID:Pyrophosphate inhibition of rho ATPase: a mechanism of coupling to RNA polymerase activity. 612 40

Mechanical overload in the heart induces two different types of adaptational mechanisms. (a) From a qualitative point of view, the maximum speed of shortening is depressed in relation to a myosin isoenzymic change responsible for decreased ATPase and, although the relaxation appears normal from a physiological point of view, the existence of an abnormality in Ca2+ uptake in the sarcoplasmic reticulum has been well documented. Both of these processes appear to improve efficiency by decreasing the heat produced per gram of tension. The existence of a large broadening of the action potential has now been well established, but it remains unexplained at the biochemical level. The functioning of mitochondria is rather controversial, and although it has been shown that they are both more abundant and smaller, the reason why their respiratory index changes remains unknown. (b) From a quantitative point of view, the adult heart adapts to overload by increasing its mass. This is mainly a consequence of a hypertrophy of the myocytes and a mitotic multiplication of nonmuscular cells. Data suggest that myocyte amitotic divisions may occur, at least in humans, and perhaps in very sizeable experimental hypertrophy. To this phenomenon has been added the development of polyploidy of myocyte nuclei, which seems to be specific to certain species. The stimulation of protein synthesis occurs very soon after pressure overload, and is delayed in volume overload; protein lysis also increases, although this is controversial. The process occurs whatever the proteins. This is accompanied by increased nuclear activity and a stimulation in RNA synthesis, which is especially precocious for messenger RNA. Among the very early events which could be potential signals for protein synthesis, attention has been focused on polyamine, RNA polymerase, and uridine kinase. The trigger mechanism, of course remains hypothetical. As a trigger for protein synthesis, several data suggest an increase in wall stress and stretch; a drop in efficiency is suggested as a trigger for qualitative changes.
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PMID:Biology of cardiac overload. 621 32

An M13 phage deletion mutant, M13 delta E101, developed as a vector for selecting DNA sequences that direct DNA strand initiation on a single-stranded template, has been used for cloning restriction enzyme digests of phi X174 replicative-form DNA. Initiation determinants, detected on the basis of clear-plaque formation by the chimeric phage, were found only in restriction fragments containing the unique effector site in phi X174 DNA for the Escherichia coli protein n' dATPase (ATPase). Furthermore, these sequences were functional only when cloned in the orientation in which the phi X174 viral strand was joined to the M13 viral strand. A 181-nucleotide viral strand fragment containing this initiation determinant confers a phi X174-type complementary-strand replication mechanism on M13 chimeras. The chimeric phage is converted to the parental replicative form in vivo by a mechanism resistant to rifampin, a specific inhibitor of the normal RNA polymerase-dependent mechanism of M13. In vitro, the chimeric single-stranded DNA promotes the assembly of a functional multiprotein priming complex, or primosome, identical to that utilized by intact phi X174 viral strand DNA. Chimeric phage containing the sequence complementary to the 181-nucleotide viral strand sequence shows no initiation capability, either in vivo or in vitro.
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PMID:Selective cloning of a DNA single-strand initiation determinant from phi X174 replicative-form DNA. 622 69

The effect of Shope fibroma virus (SFV) infection on host DNA synthesis was investigated. The cytocidal strain, SFV-I, inhibited the incorporation of [3H]thymidine into nuclear DNA very shortly (2 h) after infection, whereas the noncytocidal strain, SFV-W, did so later (10 h postinfection) and to a lesser extent. Furthermore, a two- to threefold stimulation of host DNA synthesis was recorded in SFV-W-infected cells 3 to 4 h after infection. Since virion-associated nucleases have been implicated in the shutoff of host synthesis, these and other enzymatic activities were measured in purified virion preparations. The SFV strains and vaccinia virus contained equivalent amounts of DNA-dependent RNA polymerase, ATPase, and protein kinase activities. However, in SFV-W the pH 4.5 exonuclease activity was lower than in SFV-I and vaccinia virus, and the level of pH 7.8 endonuclease was almost undetectable. To test whether the lack of endonucleolytic activity had some effect on the removal of the cross-links in the parental DNA that occurs after viral penetration, the fate of the virion SFV DNA was followed. The majority (80%) of the SFV-I and SFV-W DNA molecules extracted after viral adsorption sedimented in alkaline sucrose gradients as cross-linked. After 3 h of infection, 75% of the SFV-I DNA molecules lacked cross-links, whereas 78% of the SFV-W DNA still remained cross-linked. The same results were obtained when the presence of cross-links was tested in restriction fragments. Taken together, these results indicate that virion-associated nucleases are involved in the early shutoff of host DNA synthesis and in the elimination of cross-links from the parental viral DNA.
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PMID:Shope fibroma virus. II. Role of the virion-associated nucleases. 628 6

A protein factor which stimulates DNA polymerase alpha activity on heat-denatured DNA has been purified from mouse FM3A cells. The final preparation had a specific activity of 43,000 units/mg protein and lacked detectable DNA polymerase, RNA polymerase, DNA-dependent- and independent ATPase, exo- and endodeoxyribonuclease and phosphatase activities. The stimulating factor sedimented at 2.9S in a glycerol gradient. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the glycerol gradient fraction revealed the presence of a major band of 36,000 daltons, the amount of which corresponded well with the level of stimulating activity. The stimulation by the factor was specific for heat-denatured DNA, and a little or no stimulation was observed with native DNA, ribo- and deoxyribohomopolymers and single stranded circular DNA. Alkaline sucrose gradient sedimentation analysis of the reaction products revealed that newly synthesized DNA was covalently linked to the termini of heat-denatured DNA. The average chain length of the elongated span determined by the digestion with micrococcal nuclease and phosphodiesterase II, did not differ between in the presence and absence of the stimulating factor, suggesting that the stimulation by the factor was due to the increase in the initiation frequency of DNA synthesis from the 3'-hydroxyl terminus of heat-denatured DNA.
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PMID:Purification and characterization of a factor stimulating DNA polymerase alpha activity from mouse FM3A cells. 632 2

The synthesis of RNA catalysed by RNA polymerase from Escherichia coli is terminated at specific sites on DNA templates through the action of a multimeric basic protein known as rho (refs 1, 2). Three lines of evidence suggest that an interactions of rho with the nascent RNA is important for this termination. First, rho binds strongly to RNA; second, rho expresses an RNA-dependent ATPase activity which is essential for termination; third, RNA polymerase does not terminate RNA synthesis at rho-dependent sites when the nascent RNA is digested by ribonuclease during transcription. From the fact that certain RNAs, particularly single-stranded, pyrimidine-rich polymers containing at least 10% cytidylate residues, are more effective than other RNAs at promoting rho-ATPase, it has been proposed that rho recognises specific sites oion on a mRNA transcribed from bacteriophage lambda DNA.
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PMID:A rho-recognition site on phage lambda cro-gene mRNA. 644 43

A protein has been isolated from Bacillus subtilis which has functions similar to that of transcription termination factor rho (rho) from Escherichia coli. The apparent molecular weight of the B. subtilis rho factor is about 80000-95000 as estimated by a non-denaturing polyacrylamide gel electrophoresis method. It contains two subunits with a molecular weight of 47000 as determined by sodium dodecylsulfate/polyacrylamide gel electrophoresis. The rho factor shows poly(C)-dependent beta-gamma ATPase activity and depresses the activity of RNA synthesis from B. subtilis phage rho 29 DNA template with purified B. subtilis RNA polymerase holoenzyme. The specific activity of the poly(C)-dependent ATPase of the B. subtilis rho factor was significantly less than that of the E. coli rho factor. In the presence of rho factor fewer RNA transcripts were produced overall from the rho 29 template and smaller RNA transcripts with discrete sizes were made. These results suggest that the B. subtilis rho factor can catalyze transcription termination at specific sites on rho 29 phage DNA in vitro.
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PMID:Transcription-termination factor Rho from Bacills subtilis. 644 63

Essentially all of the DNA polymerase alpha activity in CV-1 monkey cells could be extracted as an enzyme complex that used DNA substrates with a low primer:template ratio, such as denatured DNA, at least 25 times more efficiently than did purified alpha polymerase. This form of the enzyme was rapidly dissociated either by the nonionic detergent Triton X-100 or by chromatography on phosphocellulose to generate alpha polymerase and its protein cofactor complex, C1C2. Both alpha polymerase and C1C2 were then independently purified free of deoxyribonuclease, RNA polymerase, DNA ligase, and ATPase activities, and the C1C2 complex was shown to consist of at least two proteins. Purified C1C2, which exhibited no DNA polymerase activity, completely restored the ability of alpha polymerase to use denatured DNA. Although high concentrations of denatured DNA inhibited the activity of C1C2, which binds tightly to single-stranded but not double-stranded DNA, low concentrations catalyzed reconstitution of alpha polymerase with C1C2. The resulting enzyme complex was chromatographically distinct from alpha polymerase on DEAE-Bio-Gel, was no longer dependent upon addition of C1C2 in order to utilize denatured DNA as effectively as DNase I-activated DNA, and was not inhibited by high concentrations of denatured DNA. These properties of the purified reconstituted enzyme were indistinguishable from those native alpha X C1C2-polymerase.
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PMID:Preparation of DNA polymerase alpha X C1C2 by reconstituting DNA polymerase alpha with its specific stimulatory cofactors, C1C2. 688 71


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