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)

Neocarzinostatin (NCS), an antitumor protein antibiotic that causes strand scissions of DNA both in vitro and in vivo, is shown to lower the template activity of DNA for DNA polymerase Iin vitro. There is a correlation between the extent of strand scission and the degree of inhibition, maximal inhibition of the polymerase reaction being obtained under conditions promoting maximal strand scission. These effects can be related to the concentrations of NCS and of 2-mercaptoethanol and are maximized by pretreatment of the DNA with drug. Results from polymerase assays in which the amount of drug-treated DNA template was varied at a constant level of the enzyme suggest that the sites associated with NCS-induced breaks are nonfunctional in DNA synthesis but bind DNA polymerase I. The binding of the enzyme to the inactive sites is further confirmed using [203 Hg] polymerase. It is shown that the lowering of the template activity of DNA by NCS under conditions of strand scission is due to the generation of a large number of inactive sites that block, competitively, the binding of DNA polymerase to the active sites on the template. Furthermore, the inhibition of DNA synthesis, which depends on the extent of strand breakage and on the relative amounts of template and enzyme, can be reversed by increasing the levels of template or polymerase. The finding that DNA synthesis directed by poly [d(A-T)] is much more sensitive to NCS than that primed by poly [d(G-C)] suggests that the drug preferentially interacts at regions containing adenine and/or thymine residues.
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PMID:Effect of neocarzinostatin-induced strand scission on the template activity of DNA for DNA polymerase I. 13 35

Neocarzinostatin (NCS) induces repair in a xeroderma pigmentosum lymphoblastoid line deficient in the ability to repair DNA damage induced with (acetoxyacetyl-amino)fluorene. Repair was demonstrated by the induction of repair synthesis and by the disappearance of NCS-induced single-strand breaks and/or alkaline-labile sites in DNA. Estimation of NCS-induced repair patch size, based on the density shift induced in DNA by extensive shear after incubation of treated cells in medium with bromodeoxyuridine or by calculation from the extent of restoration of DNA sedimentation profiles in alkaline sucrose gradients and the amount of repair synthesis measured by the BND cellulose method, indicated that only a few nucleotides were inserted per repaired region. NCS-treated bacteriophage T7 DNA requires incubation with alkaline phosphatase to make it a substrate for DNA polymerase I. NCS-reacted T7 DNA, even after phosphatase treatment, is not a substrate for a DNA polymerase alpha obtained from human lymphoma cells. NCS-treated T7 DNA did serve as a substrate for the DNA polymerase alpha when incubated with an apurinic/apyrimidinic (AP) endonuclease with associated 5'-3'-exonuclease activity. The results suggest that NCS-induced AP sites could be intermediates for the in vivo repair synthesis.
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PMID:Repair of neocarzinostatin-induced deoxyribonucleic acid damage in human lymphoblastoid cells: possible involvement of apurinic/apyrimidinic sites as intermediates. 625 59

Neocarzinostatin (NCS) produces apurinic/apyrimidinic (AP) sites in DNA which are repaired by the AP excision repair system. Survival after NCS treatment is not determined exclusively by this repair system, presumably because of the production of other, lethal, lesions. MNNG also produces multiple lesions which may be handled by cells in different ways. In E. coli, MNNG treatment results in rapid induction of a system which removes O6-methylguanine. Inhibition of this induction with chloramphenicol results in a large increase in mutation frequency. Induction of an enzyme which removes O6-methylguanine probably accounts for the enrichment of mutations near DNA growing points. MNNG also induces multiple closely linked mutations. The production of multiple mutations but not of single-site mutations is blocked in rec A and uvr E strains. The exact nucleotide site at which DNA synthesis is blocked in vitro by reaction with mutagens can be observed in a phi X174 system in which the nucleotide sequence is known. DNA polymerase I catalyzed synthesis is blocked one nucleotide before the reacted base on the template strand. In contrast, with some damaged templates, AMV reverse transcriptase can insert a base at the level of the reacted nucleotide on the template.
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PMID:Role of cellular systems in modifying the response to chemical mutagens. 645 18

Neocarzinostatin (NCS), which causes DNA strand scission both in vitro and in vivo, reversibly inhibits the growth of both unpermeabilized and lysolecithin-permeabilized P815 mast cells (mouse leukemic cells). Kinetic experiments with NCS-pretreated cells revealed that the permeabilized cells are more strongly affected than the unpermeabilized cells, indicating that the membrane protects the cells against the influence of NCS. The two major DNA polymerase activities (form alpha and form beta) were determined in permeabilized cells during the lag phase of growth, after NCS treatment, and an 8.5-fold higher DNA polymerase beta activity was observed in NCS-treated cells than in controls. The activity of the second enzyme, DNA polymerase alpha, was low during the period of cell proliferation.
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PMID:Stimulation of DNA polymerase beta activity in permeabilized mouse P815 mast cells after neocarzinostatin treatment. 645 62