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)

Poly (2-azaadenylic acid) [(aza2A)n] and poly(2-azainosinic acid [(aza2I)n], two newly synthesized analogues of (A)n and (I)n, in which CH-2 of the purine ring is replaced by a nitrogen atom, have been evaluated in various biological assay systems. (Aza2A) n formed a complex with (U)n and (br5U)n, and (aza2I)n formed a complex with (C)n and (br5C)n, but these complexes were markedly destabilized relative to the corresponding (A)n or (I)n complexes. The (aza2A)n-and (aza2I)n-derived complexes failed to stimulate the production of interferon in primary rabbit kidney cells and human diploid fibroblasts, under conditions (A)n. (U)n, (I)n. (C)n and (I)n. (br5C)n induced high amounts of interferon. both (aza2A)n and (aza2I)n exerted a marked inhibitory effect on the endogenous RNA directed DNA polymerase (reverse transcriptase) activity associated with murine leukemia virus. They caused a relatively mild inhibition of complement activity in an hemolytic assay system.
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PMID:Biologic activities of poly (2-azaadenylic acid) and poly (2-azainosinic acid). 7 66

Sakakibara and Tomizawa (1974a) have described a soluble in vitro system that can carry the semi-conservative replication of the Co1 E1 plasmid. However, the usefulness of this system is restricted by its rapid inactivation during storage. This paper describes a stable soluble system prepared by freeze-thaw lysis of chloramphenicol-treated E. coli cells which replicates added Co1 E1 and C1o DF13 DNA. It differs from the system employed by Sakakibara and Tomizawa in two important points: (1) Its replicative capacity for Co1 E1 DNA is by an order of magnitude higher and (2) it can be stored in liquid nitrogen for several months without loss of activity Plasmid replication in vitro is dependent of DNA polymerase I and requires de novo RNA synthesis. It is completely inhibited by rifampicin, oxolinic acid, and novobiocin. The DNA synthesized during a 60 min incubation at 30 degrees C consists mostly of monomeric supercoils. If Co1 E1 DNA is used as template, a minor portion of the label is also found in closed dimeric catenanes. Density labelling experiments indicate that plasmid DNA synthesis occurs by a semi-conservative replication process.
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PMID:Replication of small plasmids in extracts of Escherichia coli. 78 16

Pituitary growth hormone (GH) has considerable potential as an anabolic agent in animal production. For example, pigs treated with GH will grow faster (i.e. deposit protein), require less feed per unit of body weight gain, and will have less carcass fat than untreated animals. Lactating cows will produce more milk with less feed. It is likely, though not completely established, that young cattle will also respond to GH treatments. Most of the information on the mode of action of GH has been obtained with laboratory rather than farm animals. The hormone affects almost all aspects of metabolism although the specific mechanism for these effects is still not understood. Stimulation of protein accretion is reflected by increased nitrogen retention and incorporation of radioactive amino-acids into tissue proteins. An increased rate of protein synthesis is thought to be a result of enhanced ability of ribosomes to translate messenger RNA. GH increases polyamine synthesis by increased ornithine decarboxylase activity; RNA synthesis by increasing RNA polymerase and DNA synthesis by increased DNA polymerase. Cell division is stimulated in several tissues (e.g. muscle and lymphoid tissue). In vivo GH lowers the respiratory quotient indicating an increased oxidation of fatty acids. The numbers of fat cells do not change but the fat cells are reduced in size. The stimulating effects of GH on skeletal tissue, and perhaps other tissues as well, is mediated by the formation of at least three peptides called somatomedins. GH is a protein with a molecular weight of about 22,000 and contains 191 amino-acid residues. The amino-acid sequence varies with the species. GH isolated from one species is not always effective in a different species. Use of GH isolated from pituitaries does not appear to be economically feasible. A chemical synthesis for human GH has been accomplished. However, biological activity equivalent to the native hormone has not been unequivocally established. Synthesis of bovine or porcine GH is feasible but will be expensive. A partial sequence of GH with 39 amino-acid residues has some biological activity. Synthesis of this shorter peptide would be considerably less expensive. Since proteins generally are not active orally, an economic procedure for prolonged parenteral administration would have to be devised. Althernative approaches would be the stimulation of endogeneous production of GH with hypothalmic GH releasing factor. This factor has not been identified but is probably a small peptide. Agents such as arginine, DOPA, and prostaglandins, which are known to stimulate GH release under some conditions, could also be considered. Another approach would be the implantation of sparganum from the spirometra family (a flatworm). This treatment is known to mimic GH effects in the rat. Implantation of a GH producing tumour could also be considered. Clearly these latter suggestions are quite speculative and would present some obvious problems...
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PMID:Role of growth hormone in improving animal production. 78 72

Treatment of growing cultures of Mycobacterium smegmatis with alkylating agents (methyl methanesulphonate, ethyl methanesulphonate, nitrogen mustard, or mitomycin C) or with ultraviolet light resulted in enhanced specific activities of a DNA polymerase and of an ATP-dependent deoxyribonuclease. Similar results had previously been obtained with hydroxyurea and with iron limitation. The three of these treatments which were tested (methyl methanesulphonate, mitomycin C and hydroxyurea) produced strand breaks or alkali-labile regions in the DNA of this organism. The increased enzyme activities could be prevented by simultaneous treatment with inhibitors of protein synthesis. In contrast, treatment of the cultures with intercalating agents (ethidium bromide, acridine orange, or proflavine), 5-fluorouracil, caffeine, or nalidixic acid, inhibited DNA synthesis without increasing the enzyme activities. These treatments did not produce strand breaks in the DNA of this organism. The results support the hypothesis that, in M. smegmatis, damage to DNA induces increased synthesis of enzymes associated with DNA repair.
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PMID:Increased DNA polymerase and ATP-dependent deoxyribonuclease activities following DNA damages in mycobacterium smegmatis. 84 85

Rhodium(II) acetate, propionate, and butyrate showed a considerable variation in their antitumor activity against Ehrlich ascites tumor cells in mice, with the butyrate complex being the most active. The three complexes markedly inhibited DNA synthesis of Ehrlich ascites tumor cells in vivo. Rhodium (II) butyrate was the most potent inhibitor followed by the propionate complex. One hour after administration, rhodium(II) propionate and butyrate induce more uridine-5-3H incorporation into RNA than is seen in the controls. Equilibrium dialysis studied showed that rhodium(II) acetate-1-14C binds to single stranded DNA, poly-A, ribonuclease A, and bovine serum albumin but not to highly polymerized native calf thymus DNA, poly-G, or poly-C. In these cases binding occurred at the two axial positions of rhodium(II) acetate to a nitrogen donor in the ligands. The formation constants of the rhodium(II) acetate and propionate complexes with 5'-adenosine monophosphate were determined. The rhodium(II) propionate complex was more stable. Sedimentation and viscosity measurements of poly-A and poly-A/rhodium(II) acetate complexes indicate a high degree of intramolecular crosslinking in the rhodium(II) acetate/poly-A complex. The rhodium(II) carboxylate complexes were also found to be potent inhibitors of purified DNA polymerase I and RNA polymerase from Escherichia coli.
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PMID:Interaction of Rhodium(II) carboxylates with molecules of biologic importance. 110 39

Several novel imidotriphosphate analogues of thymidine have been synthesized and have been shown to be effective inhibitors of human immunodeficiency virus-1 reverse transcriptase (HIV-1 RT). When the alpha,beta-bridging oxygens of thymidine triphosphate (TTP) and 3'-azido-3'-deoxythymidine 5'-triphosphate (AZTTP) were replaced by a nitrogen, the resulting analogues were no longer substrates but instead became competitive inhibitors of HIV-1 RT. The most potent of the alpha,beta-imidotriphosphate derivatives tested was thymidine 5'-[alpha,beta-imido]triphosphate (TMPNPP, 1a). This analogue has a Ki value of 2.4 microM, inhibiting HIV-1 RT 400-fold more potently than it inhibits DNA polymerase I large fragment (Klenow). 3'-Azido-3'-deoxythymidine 5'-[alpha,beta-imido]triphosphate (AZTMPNPP, 1b) gave a Ki value about 10-fold greater than that for TMPNPP, indicating that a 3'-azido substituent decreases the affinity of AZTTP to HIV-1 RT relative to the normal 3'-OH substituent. Dideoxythymidine 5'-[alpha,beta-imido]triphosphate (ddTMPNPP, 1c) was intermediate in potency, giving a Ki value of 15 microM. In contrast, substitution at the beta,gamma-bridging oxygen by nitrogen did not block the enzymatic cleavage of the adjacent alpha,beta-phosphate linkage, and 3'-azidothymidine 5'-[beta,gamma-imido]triphosphate (AZTMPPNP, 1e), the 5'-[beta,gamma-imido]triphosphate analogue of AZTTP, is therefore both a substrate for and a potent inhibitor of HIV-1 RT with an observed Ki value of 87 nM. Further nitrogen substitution of the bridging oxygens in the phosphate chain decreases the inhibitory potency by approximately 10-fold, as in the case of thymidine 5'-[alpha,beta:beta,gamma-diimido]triphosphate (TMPNPNP, 1d).
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PMID:New thymidine triphosphate analogue inhibitors of human immunodeficiency virus-1 reverse transcriptase. 137 62

A polymerase stop assay has been developed to determine the DNA nucleotide sequence specificity of covalent modification by antineoplastic agents using the thermostable DNA polymerase from Thermus aquaticus and synthetic labelled primers. The products of linear amplification are run on sequencing gels to reveal the sites of covalent drug binding. The method has been studied in detail for a number of agents including nitrogen mustards, platinum analogues and mitomycin C, and the sequence specificities obtained accord with those obtained by other procedures. The assay is advantageous in that it is not limited to a single type of DNA lesion (as in the piperidine cleavage assay for guanine-N7 alkylation), does not require a strand breakage step, and is more sensitive than other primer extension procedures which have only one cycle of polymerization. In particular the method has considerable potential for examining the sequence selectivity of damage and repair in single copy gene sequences in genomic DNA from cells.
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PMID:Measurement of the sequence specificity of covalent DNA modification by antineoplastic agents using Taq DNA polymerase. 205 51

The time scale for rejoining of radiation-induced deoxyribonucleic acid (DNA) single-strand breaks was measured in the presence and absence of oxygen. The involvement of DNA polymerase I in this repair process was studied. Formation and rejoining of DNA strand breaks were measured in lambda DNA infecting lysogenic pol(+) and polA1 strains of Escherichia coli irradiated by 4 MeV electrons under identical conditions. Irradiation and transfer to alkaline detergent could be completed in less than 180 ms. The initial yields of DNA strand breaks were identical in pol(+) and polA1 host cells and four- to fivefold higher in the presence of oxygen than in nitrogen anoxia. Evidence for the existence of a very fast repair process, independent of DNA polymerase I, was not found, since no rejoining of radiation-induced DNA strand breaks was observed during incubation from 45 ms to 3 s. In pol(+) host cells most of the strand breaks produced in the presence of oxygen were rejoined within the first 30 to 40 s of incubation, whereas no rejoining could be detected within the same period of time in anoxic cells. Since no rejoining of broken lambda DNA molecules was observed in polA1 host cells, it is concluded that the synthetase activity of DNA polymerase I is involved in the rejoining of DNA breaks induced by radiation in the presence of oxygen.
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PMID:Time scale for rejoining of bacteriophage lambda deoxyribonucleic acid molecules in superinfected pol+ and polA1 strains of Escherichia coli after exposure to 4 MeV electrons. 460 87

The expression of a mouse mammary tumor virus is inducible by hormones, and the virus contains a hormone-responsive element. Viral particles and RNA-directed DNA polymerase (RDDP, EC 2.7.7.7; reverse transcriptase) are both detectable in human breast tumors but the frequency and significance of these findings are unknown. Breast tumor biopsy specimens (from either the primary site or a metastasis), frozen in liquid nitrogen at the time of surgery, were routinely obtained to determine estrogen receptor (ERP) concentration. A sample of the tissue was pulverized, homogenized and centrifuged at low speed to remove nuclei and mitochondria. The supernate was then centrifuged at 225,000 g to obtain the cytosol fraction for estrogen and progestin receptor (PgR) assays. Partially purified membranes for the RDDP assays were prepared from the high-speed pellet by discontinuous sucrose density gradient centrifugation. The RDDP assay involved measuring primer-dependent poly(dT) synthesis in the presence of poly(A) as template and oligo-(dT)12-18 as primer. To date, we have studied biopsy specimens from 46 patients with breast cancer. 27 (59%) had ERP and 23 (50%) were RDDP-positive. There was no significant correlation between ERP concentration and RDDP activity. PgR data were available on 36 of the patients; 17 (47%) were positive. No correlation between RDDP and PgR was apparent. Similarly, there was no correlation between RDDP and clinical stage of the disease.
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PMID:RNA-directed DNA polymerase activity in human breast cancer biopsy specimens. Relation to estrogen receptor protein. 620 38

Previously, mouse NIH 3T3 cells were stably transfected with human DNA polymerase beta (beta-pol) cDNA in the antisense orientation and under the control of a metallothionein promoter [Zmudzka, B.Z. and Wilson, S.H. (1990) Som. Cell Mol. Gen., 16, 311-320]. To assess the feasibility of enhancing the efficacy of chemotherapy by an antisense approach and to confirm a role for beta-pol in cellular DNA repair, we looked for increased sensitivity to DNA damaging agents under conditions where beta-pol is down-regulated in the antisense cell line. Such a sensitization is anticipated only where beta-pol is rate-limiting in a DNA repair pathway. A number of agents were tested: cis-diamminedichloroplatinum II (cisplatin); 1,3-bis(2-chloroethyl)-1- nitrosourea (BCNU); ionizing radiation and the radio-mimetic drug bleomycin; the bifunctional alkylating agents nitrogen mustard and L-phenylalanine mustard (melphalan); the monofunctional alkylating agent methyl methane sulfonate (MMS) and ultraviolet (UV) radiation. In the cases of cisplatin and UV radiation, a significant enhancement of cytotoxicity was observed. Damage as a result of both of these agents is thought to be repaired by the nucleotide excision repair (NER) pathway. The results suggest that, in this cell line, beta-pol is involved in and is rate-limiting in NER. We propose that down-regulation of beta-pol by antisense approaches might be used to enhance the cytotoxic effects of cisplatin and other DNA damaging chemotherapeutic agents.
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PMID:Strategic down-regulation of DNA polymerase beta by antisense RNA sensitizes mammalian cells to specific DNA damaging agents. 747 21


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