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 functional interaction between DNA helicase E and DNA polymerase epsilon from calf thymus has been detected which results in the extension of an upstream 3' OH through a downstream primer to the end of a synthetic template. DNA synthesis resulting in full-length extension products was dependent on the addition of DNA helicase E and hydrolysis of ATP, suggesting that displacement of the downstream primer was required. Identical reactions using DNA polymerases alpha and delta in place of DNA polymerase epsilon showed no full-length products dependent on helicase E, indicating that polymerases alpha and delta were incapable of functionally interacting with the helicase. The reaction leading to full-length extension products was time dependent and dependent on the concentration of added polymerase epsilon and helicase E. Exonucleolytic degradation of the downstream primer, or ligation of the downstream primer to the upstream 3' OH, were not responsible for the full-length products observed. Displacement of the downstream primer by DNA helicase E was not affected by the addition of polymerase epsilon to the reactions. Template dilution experiments demonstrated that DNA polymerase epsilon and helicase E were acting in concert to perform displacement synthesis. Additional evidence for functional coordination was obtained by demonstration that DNA helicase E stimulated DNA polymerase epsilon in a standard DNA synthetic assay using dA3000.dT16 as the template-primer. The results presented are consistent with the hypothesis that DNA helicase E and DNA polymerase epsilon are capable of coordinated activities that result in displacement synthesis. A functional interaction of this sort may be involved at the eukaryotic replication fork or in DNA repair.
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PMID:DNA helicase E and DNA polymerase epsilon functionally interact for displacement synthesis. 132 8

Analysis of fractions containing purified DNA polymerase epsilon from calf thymus has revealed the presence of a 5' to 3' exonuclease activity that is specific for a single strand of duplex DNA. This activity is capable of degrading a 3'-labeled oligonucleotide hybridized to M13mp18 DNA. When a second oligonucleotide primer is annealed 3 bases upstream, degradation of the downstream primer is strictly dependent on DNA synthesis from the upstream primer. Replacement of the downstream primer by an oligoribonucleotide of identical sequence results in a similar pattern of exonucleolytic activity. The activity has been highly purified and found to cosediment in glycerol gradients with a peptide of 56 kDa as judged by SDS/PAGE analysis. Effects of calf DNA polymerase alpha and delta on exonuclease activity are also observed but with differences in the pattern of products.
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PMID:A 5' to 3' exonuclease functionally interacts with calf DNA polymerase epsilon. 132 95

A helicase-like DNA unwinding activity was found in highly purified fractions of the calf thymus single-stranded DNA binding protein (ctSSB), also known as replication protein A (RP-A) or replication factor A (RF-A). This activity depended on the hydrolysis of ATP or dATP, and used CTP with a lower efficiency. ctSSB promoted the homologous DNA polymerase alpha to perform DNA synthesis on double-stranded templates containing replication fork-like structures. The rate and amount of DNA synthesis was found to be dependent on the concentration of ctSSB. At a 10-fold mass excess of ctSSB over double-stranded DNA, products of 200-600 nucleotides in length were obtained. This comprises or even exceeds the length of a eukaryotic Okazaki fragment. The ctSSB-associated DNA helicase activity is most likely a distinct protein rather than an inherent property of SSB, as inferred from titration experiments between SSB and DNA. The association of a helicase with SSB and the stimulatory action of this complex to the DNA polymerase alpha-catalyzed synthesis of double-stranded DNA suggests a cooperative function of the three enzymatic activities in the process of eukaryotic DNA replication.
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PMID:A complex between replication factor A (SSB) and DNA helicase stimulates DNA synthesis of DNA polymerase alpha on double-stranded DNA. 133 Jun 89

The incorporation of 6-thioguanine (S6G) in place of guanine proceeds readily in DNA synthesis reactions catalyzed by mammalian and bacterial polymerases. This report summarizes the consequences of such incorporation studied to date. S6G was incorporated into one strand of a defined M13mp18 phage sequence in a (+)reaction catalyzed by the Klenow fragment of Escherichia coli DNA polymerase I. After denaturation of the newly synthesized strand (containing S6G) and annealing with a reverse (-) 32P-labeled primer, polymerization catalyzed by the Klenow enzyme as well as by human DNA polymerases alpha, gamma, and delta was slowed considerably, compared with that across the corresponding guanine-containing template. To evaluate S6G-containing DNA as a substrate for DNA ligases, two oligodeoxynucleotides (19- and 20-mers) antisense to a 40-mer were synthesized so that the 40-mer coded for guanine at the 3' terminus of the 19-mer. After annealing of the synthetic oligonucleotides to form a duplex DNA containing a one-nucleotide gap (opposite cytosine in the 40-mer), the 19-mer was extended with 2'-deoxythioguanosine 5'-triphosphate using DNA polymerase, forming a nicked duplex DNA. The abilities of T4 DNA ligase and HeLa and calf thymus DNA ligase I to join the 5'-phosphate with the 3'-S6G-OH were severely inhibited, compared with the 3'-guanine-extended control. This finding suggests that incorporation of S6G at the 3' terminus of Okazaki fragments would inhibit lagging strand DNA synthesis. In other experiments, cleavage of S6G-containing DNA by some but not all restriction endonucleases progressed poorly, compared with the control guanine-containing DNA, independently of the location of S6G at recognition or cleavage sites, as previously observed by Iwaniec et al. [Mol. Pharmacol. 39:299-306 (1991)] with a different spectrum of enzymes. These findings indicate altered DNA-protein interactions due to S6G incorporation. The poor template function of S6G-containing DNA is consistent with the known delayed cytotoxicity and DNA damage previously reported to occur in S6G-treated cells.
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PMID:Consequences of 6-thioguanine incorporation into DNA on polymerase, ligase, and endonuclease reactions. 133 62

Mammalian nuclear DNA polymerases alpha and beta are lack of the proofreading 3'-->5' exonucleolytic activity. 40 and 50 kDa 3'-->5' exonucleases were isolated from rat liver. The exonucleases were shown to excise mismatched nucleotides from poly[d(A--T)] template 10 and 2 fold faster than matched ones. The addition of either exonuclease to DNA polymerase alpha from rat liver or calf thymus 5-10 times increased the accuracy of reproduction of primed DNA from bacteriophage phi X174 amber 3, values of exonuclease and DNA polymerase activities being approximately equal. The exonuclease activity surpasses the DNA polymerase one by an order of magnitude in chromatin and nuclear membrane. These data, taken together, are indicative of potent proofreading into hepatocytes.
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PMID:[3'-->5'-exonucleases of the rat liver and the correction of replication errors]. 133 91

The single-stranded DNA binding protein RP-A is required in SV40 DNA in vitro replication. The RP-A purified from calf thymus contains 4 polypeptides with molecular weights 70kDa, 53kDa, 32kDa, and 14kDa. The p70 subunit and its proteolysed form p53 are recognized by the monoclonal antibody 70C (Kenny et al. (1990)) and bind to ssDNA. The p70 and p32 subunits of bovine RP-A are phosphorylated by CDC2-cyclin B kinase. Bovine RP-A supports the origin dependent unwinding of SV40 DNA by T antigen. Furthermore, bovine RP-A can efficiently substitute for human RP-A in SV40 DNA replication in vitro. A modified blotting technique revealed that RP-A interacts specifically and directly with the p48 subunit of DNA polymerase alpha-primase complex.
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PMID:Purification and functional characterization of bovine RP-A in an in vitro SV40 DNA replication system. 133 80

By using a complementation assay that enabled DNA polymerase delta and DNA polymerase epsilon to replicate a singly-DNA primed M13 DNA in the presence of proliferating cell nuclear antigen (PCNA) and Escherichia coli single-stranded DNA binding protein (SSB), we have purified from calf thymus in a five step procedure a multipolypeptide complex with molecular masses of polypeptides of 155, 70, 60, 58, 39 (doublet), 38 (doublet) and 36 kDa. The protein is very likely replication factor C (Tsurimoto, T. and Stillman, B. (1989) Mol. Cell. Biol. 9, 609-619). This conclusion is based on biochemical and physicochemical data and the finding that it contains a DNA stimulated ATPase which is under certain conditions stimulated by PCNA. Together RF-C, PCNA and ATP convert DNA polymerases delta and epsilon to holoenzyme forms, which were able to replicate efficiently SSB-covered singly-DNA primed M13 DNA. Calf thymus RF-C could form a primer recognition complex on a 3'-OH primer terminus in the presence of calf thymus PCNA and ATP. Holoenzyme complexes of DNA polymerase delta and epsilon could be isolated suggesting that these enzymes directly interact with the auxiliary proteins in a similar way. Under optimal replication conditions on singly-DNA primed M13 DNA the DNA synthesis rate of DNA polymerase delta was higher than of DNA polymerase epsilon. Based on these functional date possible roles of these two DNA polymerases in eukaryotic DNA replication are discussed.
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PMID:Calf thymus RF-C as an essential component for DNA polymerase delta and epsilon holoenzymes function. 135 54

Proliferating cell nuclear antigen (PCNA) and PCNA-dependent DNA polymerase delta were partially purified and characterized from rabbit bone marrow. Rabbit DNA polymerase delta sediments at 8.2 S upon glycerol density gradient centrifugation. Similar to calf thymus PCNA-dependent DNA polymerase delta, a 125-123-kDa doublet and 48-kDa polypeptides correlate with DNA polymerase activity. Western blotting of rabbit DNA polymerase delta with polyclonal antibody to calf thymus PCNA-dependent DNA polymerase delta gives the same results as calf thymus delta; the 125-123-kDa doublet is recognized. PCNA-dependent DNA polymerase delta is resistant to inhibition by dideoxynucleotides and is relatively insensitive to inhibition by N2-[p-(n-butyl)phenyl]dGTP. A 3'-->5' exonuclease copurifies with the DNA polymerase. The processivity of DNA polymerase delta alone is very low but greatly increases with the addition of PCNA from rabbit bone marrow or calf thymus. Comparative studies of the original DNA polymerase delta from rabbit bone marrow demonstrate a lack of recognition by antibodies to calf thymus delta and a high degree of processivity in the absence of PCNA. Additionally, the originally described DNA polymerase delta is a single polypeptide of 122 kDa. These features would recategorize the original delta to the epsilon category by recently proposed convention. PCNA-dependent DNA polymerase delta is a relatively minor component of rabbit bone marrow compared to DNA polymerase alpha and PCNA-independent DNA polymerase delta (epsilon), the relative proportions being alpha, 60%; delta, 7%; and epsilon, 30%.
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PMID:PCNA-dependent DNA polymerase delta from rabbit bone marrow. 136 Nov 52

3'-Fluoro-2',3'-dideoxythymidine 5'-(alpha-methylphosphonyl)-beta,gamma- diphosphate and 2'-deoxythymidine-5'-(alpha-methylphosphonyl)-beta, gamma- diphosphate have been synthesized. Both compounds are incorporated into DNA chains during catalysis by reverse transcriptases of human immunodeficiency (HIV) and avian myeloblastosis (AMV) viruses, DNA polymerase beta from rat liver, terminal deoxynucleotidyl transferase from calf thymus and (at a very low rate) is by E. coli DNA polymerase I, Klenow fragment. The first compound is a termination substrate while the second is capable of multiple incorporation into the DNA chains. For instance, reverse transcriptase catalysis resulted in the appearance of 8 residues of second compound. DNA polymerases alpha and epsilon from human placenta incorporated none of the above compounds into DNA chains, although an inhibition of DNA synthesis by both compounds was observed with all enzymes mentioned. The 3'----5'-exonuclease activity of DNA polymerase I, Klenow fragment, hydrolyzed DNA fragments containing phosphonomethyl internucleoside groups, while such DNA fragments were resistant to the E. coli exonuclease III.
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PMID:Formation of phosphonester bonds catalyzed by DNA polymerase. 137 65

Poly(L-malate) is an unusual polyanion found in nuclei of plasmodia of Physarum polycephalum. We have investigated, by enzymatic and fluorimetric methods, whether poly(L-malate) and structurally related polyanions can interact with DNA-polymerase-alpha-primase complex and with histones of P. polycephalum. Poly(L-malate) is found to inhibit the activities of the DNA-polymerase-alpha-primase complex and to bind to histones. The mode of inhibition is competitive with regard to DNA in elongation and noncompetitive in the priming of DNA synthesis. Spermidine, spermine, and histones from P. polycephalum and from calf thymus bind to poly(L-malate) and antagonize the inhibition. The polyanions poly(vinyl sulfate), poly(acrylate), poly(L-malate), poly(D,L-malate), poly(L-aspartate), poly(L-glutamate) have been examined for their potency to inhibit the DNA polymerase. The degree of inhibition is found to depend on the distance between neighboring charges, given by the number of atoms (N) interspaced between them. Poly(L-malate) (N = 5) and poly(D,L-malate) (N = 5) are the most efficient inhibitors, followed by poly(L-aspartate) (N = 6), poly(acrylate) (N = 3), poly(L-glutamate) (N = 8), poly(vinyl sulfate) (N = 3). It is proposed that poly(L-malate) interacts with DNA-polymerase-alpha-primase of P. polycephalum. According to its physical and biochemical properties, poly(L-malate) may alternatively function as a molecular chaperone in nucleosome assembly in the S phase and as both an inhibitor and a stock-piling agent of DNA-polymerase-alpha-primase in the G2 phase and M phase of the plasmodial cell cycle.
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PMID:Specific inhibition of Physarum polycephalum DNA-polymerase-alpha-primase by poly(L-malate) and related polyanions. 137 54


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