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:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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 Chinese hamster V79 cell mutant aphr-4-2, selected for its resistance to aphidicolin, a specific inhibitor of DNA polymerase alpha (DNA nucleotidyltransferase, EC 2.7.7.7), is characterized by slow growth, UV sensitivity, and hypersensitivity to UV-induced mutation. DNA polymerase alpha has been purified from mitochondria-free crude extracts of the mutant and its parental wild-type cells by sequential column chromatography on DEAE-cellulose and phosphocellulose. The major DNA polymerase activity from both cell lines was found to have characteristics of the alpha-type polymerase: sensitivity to 0.2 M KCl, resistance to heat denaturation (45 degrees C for 15 min), an apparent Km of 5 microM for dATP, and an ability to copy poly(dT)X(rA)10 but not poly(rA)X(dT)12. The crude extracts and purified DNA polymerase alpha from the mutant cells are not inhibited by aphidicolin (greater than 0.6 microM). The apparent Km for dCTP with DNA polymerase alpha is 1.0 +/- 0.4 microM (mean +/- SD) for the mutant enzyme. The polymerase from the parental cells, similarly purified, is sensitive to aphidicolin and has an apparent Km for dCTP of 10 +/- 4 microM. The spontaneous mutation rate (per cell per division), determined by fluctuation analysis at the Na+/K+-ATPase (EC 3.6.1.8) locus, is higher for mutant cells (42-73 x 10(-8)) than for parental cells (3-16 x 10(-8)). These data suggest a mechanism for aphidicolin resistance of the mutant--i.e., a decrease in the Km for dCTP. The results also indicate that an altered DNA polymerase alpha may be intrinsically mutagenic during normal semiconservative replicative as well as during UV-induced repair syntheses.
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PMID:Mammalian mutator mutant with an aphidicolin-resistant DNA polymerase alpha. 640 75

Phage phi 29 terminal protein, p3, essentially pure, was isolated in a denatured form from viral particles, and anti-p3 antiserum was obtained. A radioimmunoassay to detect and quantitate protein p3 was developed. By using this assay, native protein p3 was highly purified from Escherichia coli cells harboring a gene 3-containing recombinant plasmid. After three purification steps, the protein was more than 96% pure; its amino acid composition was very similar to that deduced from the nucleotide sequence of gene 3. The purified protein was active in the formation of the covalent p3-dAMP initiation complex when supplemented with extracts of B. subtilis infected with a sus mutant of phi 29 in gene 3. No DNA polymerase or ATPase activities were present in the final preparation of protein p3.
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PMID:Purification in a functional form of the terminal protein of Bacillus subtilis phage phi 29. 642 20

At an early purification stage, DNA polymerase alpha holoenzyme from calf thymus can be separated into four different forms by chromatography on DEAE-cellulose. All four enzyme forms (termed A, B, C, and D) are capable of replicating long single-stranded DNA templates, such as parvoviral DNA or primed M13 DNA. Peak A possesses, in addition to the DNA polymerase alpha, a double-stranded DNA-dependent ATPase, as well as DNA topoisomerase type II, 3'-5' exonuclease, and RNase H activity. Peaks B, C, and D all contain, together with DNA polymerase alpha, activities of primase and DNA topoisomerase type II. Furthermore, peak B is enriched in an RNase H, and peaks C and D are enriched in a 3'-5' exonuclease. DNA methylase (DNA methyltransferase) was preferentially identified in peaks C and D. Velocity sedimentation analyses of the four peaks gave evidence of unexpectedly large forms of DNA polymerase alpha (greater than 11.3 s), indicating that copurification of the above putative replication enzymes is not fortuitous. With moderate and high concentrations of salt, enzyme activities cosedimented with DNA polymerase alpha. Peak C is more resistant to inhibition by salt and spermidine than the other three enzyme forms. These results suggest the existence of a leading strand replicase (peak A) and several lagging strand replicase forms (peaks B, C, and D). Finally, the salt-resistant C form might represent a functional DNA polymerase alpha holoenzyme, possibly fitting in a higher-order structure, such as the replisome or even the chromatin.
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PMID:Mammalian DNA polymerase alpha holoenzymes with possible functions at the leading and lagging strand of the replication fork. 658 75

DNA polymerase III holoenzyme (holenzyme) has an ATPase activity elicited only by a primed DNA template. Reaction of preformed ATP.holoenzyme complex with a primed template results in hydrolysis of the ATP bound to the holoenzyme, release of ADP and Pi, and formation of an initiation complex between holoenzyme and the primed template. Approximately two ATP molecules are hydrolyzed for each initiation complex formed, a value in keeping with the number bound in the ATP.holoenzyme complex. The possibility that the latter and the initiation complex contain two holoenzyme molecules is supported by the presence of two beta monomers in the initiation complex. Holoenzyme action in the absence of ATP resembles that of pol III (the holoenzyme core) or DNA polymerase III (holoenzyme lacking the beta subunit), with or without ATP, in sensitivity to salt and in processivity of elongation. The initiation complex formed by ATP-activated holoenzyme resists a level of KCl (150 mM) that completely inhibits nonactivated holoenzyme and the incomplete forms of the holoenzyme, and displays a processivity at least 20 times greater. Upon completing replication of available template, holoenzyme can dissociate and form an initiation complex with another primed template, provided ATP is available to reactivate the holoenzyme. By inference, no essential subunits are lost in the cycle of initiation, elongation and dissociation.
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PMID:ATP activation of DNA polymerase III holoenzyme from Escherichia coli. II. Initiation complex: stoichiometry and reactivity. 674 41

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

An enzymatic activity that synthesizes oligoribonucleotides in lengths of 9-10 nucleotides and multiples thereof has been purified over 10,000-fold from mouse hybridoma cells. The oligoribonucleotides serve as primers to initiate DNA synthesis, and the activity has properties expected of mammalian DNA primase. The most highly purified fraction has two major protein components, as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, of 56,000 and 46,000 Da. These proteins co-purify in a 1:1 stoichiometry along with oligoribonucleotide synthesis activity and with an activity that initiates the synthesis of DNA by DNA polymerase alpha. The sedimentation coefficient on glycerol gradients is 5.5 S, and this is consistent with one 56,000- and one 46,000-Da subunit/native enzyme. No DNA polymerase activity was detected in the most highly purified fraction. Poly(dIT) is the most active template, whereas a variety of single-stranded DNA templates are 10-15% as active and double-stranded DNA templates are 10-15% as active and double-stranded DNA is less than 1%. rATP is an absolute requirement as is Mg2+. No ATPase activity was detected with or without addition of DNA, single- or double-stranded. (NH4)2SO4 and NaPO4 buffer, pH 7.6, are inhibitory above 20 mM, whereas KCl is inhibitory above 80 mM. beta-D-arabinose-CTP is a strong inhibitor of primase; approximately 50% inhibition is observed when present at one-fifth the concentration of rCTP.
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PMID:A DNA primase from mouse cells. Purification and partial characterization. 688 74

We have recently developed an in vitro DNA synthesis system in which a synthetic heptaribonucleotide pairs with a unique site on a single-stranded fd DNA molecule and thereby primes the growth of new DNA strands from this single point (Huang, C.-C., and Hearst, J. E. (1980) Anal. Biochem. 103, 127-139). In this report, we use this system to investigate the mechanism by which various bacteriophage T4 DNA replication proteins stimulate the T4 DNA polymerase. We find that with the "polymerase accessory proteins" present (the T4 gene 44/62 and 45 proteins), the DNA polymerase proceeds rather rapidly through the occasional hairpin helices which otherwise interrupt the progress of this enzyme along single-stranded DNA templates. By using a potent inhibitor of the 44/62 ATPase, ATP gamma S (adenosine 5'-O-(3-thiotriphosphate)), we have obtained data which suggest that ATP hydrolysis is required for the formation of a polymerase accessory protein-DNA template complex, and that this complex then persists, serving as a sliding clamp which greatly increases the strength of binding between a T4 DNA polymerase molecule and its 3'OH primer template end. The progress of the T4 DNA polymerase though hairpin helices in the DNA template is also stimulated by addition of the T4 helix-destabilizing protein (gene 32 protein). The effect of the 44/62 and 45 proteins is independent of the effect of the 32 protein in this assay, and the rate of polymerase travel over the strongest hairpin helices is increased more than 40-fold in the presence of these four additional proteins.
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PMID:Two types of replication proteins increase the rate at which T4 DNA polymerase traverses the helical regions in a single-stranded DNA template. 697 Dec 92

In the framework of the mycobacterial genome sequencing project, a continuous 37,049 bp sequence from the Mycobacterium leprae chromosome has been determined. Computer analysis revealed 10 complete open reading frames, and nine of their products show similarity to known proteins. Seven of these were identified as the enzyme isocitrate lyase, two P-type ATPase cation transporters, two AMP-binding proteins, the ribosomal protein S1, and DNA polymerase I. Interestingly, the polA gene, encoding DNA polymerase, is flanked by two inverted copies of a new class of the M. leprae specific repetitive sequence, RLEP, and this structure resembles a transposable element. A second copy of this element was found at another locus in the genome, but the two copies were not present in equal amounts and could not be found in all isolates of M. leprae. This is the first evidence for genomic variability in the leprosy bacillus and might ultimately be useful for developing a molecular test capable of distinguishing between strains of M. leprae.
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PMID:The Mycobacterium leprae genome: systematic sequence analysis identifies key catabolic enzymes, ATP-dependent transport systems and a novel polA locus associated with genomic variability. 747 88

The DNA polymerase III (pol III)holoenzyme is the 10 subunit replicase of Escherichia coli. The 71 kDa tau subunit, encoded by dnaX, dimerizes the core polymerase (alpha epsilon theta) to form pol III'[(alpha epsilon theta)2 tau 2]. tau is also a single-stranded DNA-dependent ATPase and can substitute for the gamma subunit during initiation complex formation. We show here that tau also possesses a DNA-DNA and RNA-DNA annealing activity that is stimulated by Mg2+, but neither requires ATP nor is inhibited by non-hydrolyzable ATP analogs. This suggests the tau may act to stabilize the primer-template interaction during DNA replication.
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PMID:DNA and RNA-DNA annealing activity associated with the tau subunit of the Escherichia coli DNA polymerase III holoenzyme. 753 62


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