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)

The effect of bleomycin on [3H]thymidine 5'-triphosphate ([3H]TTP) incorporation into isolated sucrose nuclei from host liver and Morris hepatomas has been compared. Bleomycin stimulates [3H]TTP incorporation 13-fold in host liver and hepatoma 16 nuclei, 8-fold in hepatoma 7800 nuclei, and 3-fold in hepatoma 7777 nuclei. Differences in the nuclear membranes are not responsible for the different response of the nuclei. Nuclei, denuded of their membranes by Triton X-100 treatment, give similar results to sucrose nuclei. Analysis of DNA extracted from liver or hepatoma nuclei incubated with bleomycin indicates that bleomycin produces scissions in the nuclear DNA and that some repair synthesis takes place. Incubation of nuclei with 111indium-labeled bleomycin shows an equal binding capacity of liver and hepatoma nuclei for bleomycin. Bleomycin also stimulates incorporation of [3H]TTP in a system using chromatin or calf thymus DNA as primer. Host liver or hepatoma chromatin incubated with a DNA polymerase extracted from normal rat liver nuclei is stimulated approximately to the same extent by bleomycin. When DNA polymerase extracts from host liver and hepatoma nuclei are assayed with calf thymus DNA as primer, bleomycin has a greater stimulatory effect on [3H]TTP incorporation with host liver DNA polymerase than with hepatoma DNA polymerase in the system. We suggest that a defect in the repair system in hepatoma nuclei is responsible for the relatively lower response to bleomycin.
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PMID:Effect of bleomycin on [3H]Thymidine 5'-Triphosphate incorporation into host liver and hepatoma nuclei. 5 97

The antibiotic bleomycin stimulates deoxyribonucleic acid (DNA) synthesis in toluene-treated Escherichia coli cells. The increase in synthesis is linear with bleomycin concentration. Bleomycin-stimulated DNA synthesis is independent of replication and dependent on DNA polymerase I. Replication is spared as the DNA polymerase I-dependent DNA synthesis increases. Bleomycin does not appear to have any effect on purified E. coli DNA polymerases I or II. Our results suggest that bleomycin causes nicking of the bacterial chromosome with subsequent DNA synthesis catalyzed by DNA polymerase I.
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PMID:Effect of bleomycin on deoxyribonucleic acid synthesis in toluene-treated Escherichia coli cells. 5 40

A method for the determination of the Bleomycin-inactivating enzyme is described. The amount of conversion of active Bleomycin to inactive Bleomycin is used as a measure for the determination of the Bleomycin-inactivating enzyme activity. The active Bleomycin is determined in a DNA-dependent DNA polymerase assay; in a certain Bleomycin concentration range the resulting reduction of the activity of the DNA-dependent DNA polymerase is correlated linearly when plotted semilogarithmically. By application of this method it has been found that the activity of the Bleomycin-inactivating enzyme is highest in liver and present in lower concentrations in testis, spleen, lung, brain, and skin.
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PMID:Determination of the bleomycin-inactivating enzyme in biopsies. 6 6

Bleomycin (BLM) exclusively affects thymidine-containing compounds such as DNA and polydeoxyribonucleotides by releasing free thymine and leaving aldehyde functions. Molecular morphology and base sequence of the DNA strongly influence BLM activity. High BLM concentrations, besides modifying DNA into oligothyminic or athyminic nucleic acids, cause strand scissions. Enzymatic DNA and RNA synthesis is strongly influenced by BLM. The inhibition in DNA-dependent DNA polymerase and DNA-dependent RNA polymerase assays is of the non-competitive type. Protein biosynthesis in in vitro systems is not affected by BLM even at high concentrations. BLM turns out to be a strong inhibitor of DNase I and of DNase II; the inhibition is of the competitive type. The enzymatic activities of nucleases using RNA as substrate (RNase A, RNase B, Rnase T1, venom phosphodiesterase I and spleen phosphodiesterase II) are not influenced by this antibiotic. The antibiotic reduces cell proliferation (L5178y mouse lymphoma cells) in vitro in low concentrations by cytostasis and at higher concentrations by cytotoxicity. In BLM-treated L5178y cells, DNA synthesis is strongly reduced, while RNA and protein synthesis are not affected. In vivo, using growing quail oviducts, cell proliferation and cytodifferentiation are markedly inhibited after BLM treatment. This is attributed to the observed inhibition of DNA synthesis. RNA and protein synthesis as well as gene expression are not influenced by BLM under the conditions used. The selective inhibition of DNA synthesis in vivo may be caused by the following mechanisms: (1) competition of BLM with RNA; (2) blocking of the accessibility of DNA in chromatin to BLM, and (3) dependence from the repair processes. BLM inhibits growth of sarcomas, induced by oncogenic RNA viruses in vivo; well-developed tumours show regression after BLM treatment. Transformation of chick embryo fibroblasts by oncogenic RNA viruses in vitro and growth of these viruses is blocked by BLM; the most sensitive period for BLM inhibition is the time during the first period (integration of viral genome into cellular genome?) after infection.
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PMID:Effect of bleomycin on DNA, RNA, protein, chromatin and on cell transformation by oncogenic RNA viruses. 6 69

Bleomycin inhibited the ligase, which was partially purified from rat ascites hepatoma, AH-130, even at a concentration as low as 0.01-1 mug/ml. The DNA degraded by bleomycin was not repaired by ligase. Therefore, it was suggested that bleomycin at higher concentration produced strand scission of DNA, which could not be repaired by the ligase, and at lower concentration inhibited the ligase reaction presumably by binding to DNA strand or to ligase. Also, the specificity of inhibition by bleomycin on the DNA polymerase of oncogenic RNA virus was tested, comparing with the four kinds of DNA polymerases extracted from the spleen of mice infected with Friend virus. Three kinds of DNA polymerases from spleen were not inhibited by bleomycin, but the fourth enzyme, which was induced in the spleen by virus infection, was inhibited by the antibiotic, when poly-d(AT) and poly-dG with dC were used as template.
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PMID:Actions of bleomycin on DNA ligase and polymerases. 6 70

The N syndrome is characterized by mental retardation, malformations, chromosome breakage, and development of T-cell leukemia (Opitz et al.: Proceedings of the II International Congress IASSMD pp 115-119, 1971; Hess et al.: Clinical Genetics 6:237-246, 1974b, American Journal of Medical Genetics [supplement] 3:383-388, 1987). N syndrome fibroblasts were studied to see if the high chromosome breakage rate associated with this apparently X-linked syndrome could be related to a deficiency of DNA polymerase alpha, a product of a gene localized to the X chromosome. Bleomycin, which is known to break double-stranded DNA, produced increased chromosome breakage in normal control, Fanconi anemia, and N syndrome fibroblasts. When aphidicolin was used to inhibit repair mediated by DNA polymerase alpha, both normal control and Fanconi anemia fibroblasts showed significantly more chromosome breakage than was produced by bleomycin alone, but there was no increase in the amount of breakage seen in the N syndrome fibroblasts over that seen with bleomycin alone. This suggests that the N syndrome is due to a mutation affecting the region of the X chromosome on which the gene for DNA polymerase alpha is located, and that the high risk of T-cell leukemia observed in the hemizygote is due to this DNA repair defect.
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PMID:DNA polymerase alpha defect in the N syndrome. 168 58

Bleomycin-induced DNA repair synthesis in the permeabilized HeLa cells was sensitive to aphidicolin, an inhibitor of DNA polymerase alpha and delta, and to dideoxythymidine triphosphate (ddTTP), a specific inhibitor of DNA polymerase beta. Upon combined treatment with these inhibitors, the DNA repair synthesis was inhibited to an even higher degree. This indicated that the aphidicolin- and ddTTP-sensitive DNA repair syntheses may occur by independent mechanisms. The structure of incomplete repair patches being accumulated in the presence of these inhibitors was investigated by digestion of DNA with exonuclease III after incubation with Klenow fragment and T4 DNA ligase. The results have suggested that the patch accumulating in the presence of aphidicolin is a single-stranded gap made by excision enzyme(s), whereas that accumulating in the presence of ddTTP may be generated by strand displacement.
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PMID:Two different mechanisms are involved for the bleomycin-induced DNA repair synthesis in permeabilized HeLa cells. 248 Jan 15

DNA damaging agents such as nitrosoureas are widely used for the treatment of malignant gliomas. Therefore, quantitative measurement of DNA damages induced by antineoplastic drugs is useful to judge the efficacy of the drug and understand the pharmacological action of the drug. We have utilized in situ nick translation method to demonstrate "nicks" in DNA of glioma cells treated by various antineoplastic agents. Exponentially growing rat 9 L glioma cells (4 x 10(4] were seeded in the chamber slide. After fourty eight hours, the medium was changed to that containing various concentration of the drug (ACNU, cis-DDP, BLM, ADM and VP-16) and the cell was treated for 1 hour. Then, the cell was fixed for 10 minutes in methanol-acetic acid (v/v 3:1). Following fixation, the cell was incubated in the nick translation mixture containing E. coli DNA polymerase I, 3H-TTP, and 4 dNTP's (ATP, GTP, CTP, CTP and TTP) for 10 minutes at room temperature. The slide was dipped in the autoradiographic emulsion, exposed for 4 days at 4 degrees C, and then developed, the number of the silver grains over nuclei was counted under the microscope. For comparison of the effect of the drug to glioma cells, IC50 (inhibitory concentration of the drug for 50% cell kill) of each drug was determined by treating the cell for 48 hours at the various concentration of the drug. Small number of the silver grains was noted in cells with no treatment. Over IC50 as the concentration of the drug increased, the number of the nick increased in cells treated with bleomycin or adriamycin which are known to produce single strand breaks in DNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[In situ nick translation for detection of DNA damages in glioma cells]. 262 7

Isolated trout liver cells were treated with lysolecithin to produce an in situ system for characterizing DNA repair in teleosts. In this preparation, the integrity of the plasma membrane is altered, nuclei remain intact, and the concentrations of dNTPs and nucleotide analogs, which normally do not penetrate intact plasma membranes, can be controlled. Following lysolecithin treatment, 50% of the total cellular protein and nearly 75% of total lactate dehydrogenase activity was released from the liver cells. Microscopic examination indicated that the integrity of the plasma membrane of trout hepatocytes was disrupted by lysolecithin; however, smaller nonhepatocytic liver cells were resistant to the disrupting effects of this detergent. Bleomycin induced DNA repair synthesis in lysolecithin-treated cells, as demonstrated by CsCl gradient analysis of 5-bromo, 2'-deoxyuridine, 5'-triphosphate-labeled DNA. Optimal conditions for bleomycin-induced DNA repair synthesis in lysolecithin-treated trout liver cells were considerably different from that in lysolecithin-treated mammalian cells. Bleomycin-induced DNA repair synthesis was lower in lysolecithin-treated trout liver cells than in lysolecithin-treated mammalian cells at identical concentrations of 2'-deoxyribonucleoside, 5'-triphosphates (dNTPs), suggesting the decreased sensitivity of trout cells in unscheduled DNA synthesis assays can be attributed to factors other than differences in dNTP pools. Bleomycin-induced DNA repair synthesis in trout hepatocytes was shown to be very sensitive to inhibition by 2', 3'-dideoxythymidine, 5'-triphosphate and was resistant to inhibition by cytosine arabinoside, 5'-triphosphate, butylphenyldeoxyguanosine, 5'-triphosphate and aphidicolin. These observations indicate repair of bleomycin-induced DNA damage in trout cells occurs through a mechanism similar to that in mammalian cells, utilizing DNA polymerase beta.
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PMID:DNA repair synthesis in isolated rainbow trout liver cells. 272 Sep 10

Analysis of sister chromatid exchanges (SCEs) is widely used as an assay for mutagenic carcinogens. Visualization of SCEs generally requires that the cells be cultured for 2 cycles of replication with the thymidine analog bromodeoxyuridine (BrdUrd). To see if incorporation of BrdUrd into chromosomal DNA influences the SCE response after treatment with chemical compounds, we have studied the effect of BrdUrd incorporation on SCEs induced by 5 different chemicals: bleomycin (BLM), which causes DNA single- and double-strand breakage; proflavine (PF), which intercalates into DNA; mitomycin C (MMC), a polyfunctional alkylating agent that cross-links DNA and also forms monoadducts; and 2 chemicals that do not appear to interact with DNA directly, aphidicolin (APC), an inhibitor of DNA polymerase alpha; and 3-aminobenzamide (3AMB), an inhibitor of poly-(ADP-ribose)-polymerase. Chemical treatment was for the first, second, or both cell cycles, and BrdUrd was present for the first or both cell cycles. All treatments with BLM, PF, or MMC increased the SCE frequency independently of the BrdUrd labeling protocol. With APC and 3AMB, on the other hand, only small increases in SCE frequency were observed when treatment was for the first cell cycle, but there were far greater increases when the chemical was present for the second or for both successive cell cycles. To further determine at which cycle SCEs were formed after continuous treatment of cells with BrdUrd and a test chemical, we also examined the induction of SCEs in the first cell cycle (twins) and in the second cell cycle (singles) in tetraploid cells. Bleomycin, PF, and APC induced almost equal numbers of SCEs in both cell cycles, but MMC appeared to induce more SCEs in the second cycle than in the first. This is probably caused by long-lived lesions that induce SCEs. 3-Aminobenzamide, which does not form persisting lesions, also induced more single than twin SCEs, suggesting that this compound affects BrdUrd-substituted DNA differently than it does unsubstituted DNA. This type of interaction between a chemical and BrdUrdsubstituted DNA should be taken into consideration when SCE analysis is used as an assay system.
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PMID:Effect of bromodeoxyuridine on induced sister chromatid exchanges. 608 62


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