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 single peak of DNA polymerase activity was detectable by phosphocellulose chromatography of leukemic guinea pig lymphoblast whole cell extracts. The inability to detect multiple peaks of activity as described with other cell types is shown to be due to the insolubility of a large proportion of the DNA polymerase activity under the extraction condition used. Multiple forms of DNA polymerase with different template specificities were recognized in extracts of the subcellular fractions of these cells after chromatography on phosphocellulose and DEAE cellulose. On Sephadex G-200 gel filtration these enzymes had apparent molecular weights in excess of 140,000 daltons. No RNA polymerase (reverse transcriptase) was detected in any subcellular fraction despite the presence of oncornavirus like particles in these cells.
Cancer Biochem Biophys 1978
PMID:Studies of the template preference and other characteristics of the DNA polymerases of leukemic guinea pig lymphoblasts. 29

The mutagenicity of 99 chemicals was determined in a standard Salmonella typhimurium assay with the use of strains TA1535 and TA1538; the DNA-modifying capacity was determined with normal and DNA polymerase-deficient Escherichia coli strains. The following categories of chemicals were studied: alkylating agents (15); nitrosamines, hydrazines, and related substances (8); heterocyclics (10); aromatic amines (36); polycyclic aromatic hydrocarbons (11); amides, ureas, and acylating agents (7); antimetabolites (5); inorganics (4); and promoters (3). Of the substances studied, 21 were known noncarcinogens, 21 were ultimate carcinogens, and 45 were procarcinogens. Of the noncarcinogens, 35, 30, and 25% were positive in the Salmonella, E. coli, and both systems, respectively. All of the ultimate carcinogens were detectable as mutagens of DNA-modifying agents; 79, 100, and 79% gave positive tests in the Salmonella, E. coli, and both systems, respectively. Of the procarcinogens 72% were identifiable by these procedures: 52, 67, and 48% in the Salmonella, E. coli, and both assays, respectively. A tabulation of the combined data for ultimate carcinogens and procarcinogens indicates that 77% of the carcinogens gave positive results: 61, 74, and 59% in the Salmonella, E. coli, and both assays, respectively. We suggest that, for prescreening procedures with microbial assays, S. typhimurium strains TA98 and TA100 be included and the standard E. coli DNA polymerase-deficient assay be run in tandem with the Salmonella mutagenicity assay. When the standard E. coli DNA polymerase-deficient assay does not give interpretable results because of the lack of zones of growth inhibition, a modified assay with the use of liquid suspension should be performed.
J Natl Cancer Inst 1979 Apr
PMID:Evaluation of the mutagenicity and DNA-modifying activity of carcinogens and noncarcinogens in microbial systems. 37 56

The capacity of human cells to modulate the synthesis of DNA repair enzymes has been investigated by measuring the induction of the uracil-DNA glycosylase during lymphocyte stimulation. Treatment of peripheral lymphocytes with phytohemagglutinin increased glycosylase activity 10-fold. Glycosylase stimulation was coordinate with the activation of DNA synthesis and DNA polymerase activity. Two chromatographically distinct species of the glycosylase have been resolved; only one species is induced during phytohemagglutinin stimulation. The effect of actinomycin D and cycloheximide on glycosylase induction was determined. Treatment with either inhibitor at 96 hr after phytohemagglutinin addition (maximal induction) decreased glycosylase activity after an appreciable lag period. This suggested that induction of the uracil-DNA glycosylase requires transcription and translation although the enzyme may be quite stable once induced.
Cancer Res 1979 Jun
PMID:Induction of the DNA repair enzyme uracil-DNA glycosylase in stimulated human lymphocytes. 44 5

The effect of methylprednisolone (MP) on the cell kinetic response to cyclophosphamide (CP) and Adriamycin (ADR) in C3H/HeJ spontaneous mammary tumors and hematopoietic tissue was investigated. The [3H]deoxythymidine labelingg index, the primer-dependent DNA polymerase labeling index (an estimate of tumor growth fraction), and the mitotic index were determined at various intervals after treatment. Treatment consisted of CP (200 mg/kg) on Day 0 plus ADR (2 mg/kg) on Day 1 with or without MP every 12 hr for 9 doses beginning on Day 2. In tumors treated with CP and ADR alone, changes in the kinetic parameters suggested proliferative recovery between Days 3 and 4 which coincided with bone marrow recovery. In tumors treated with CP, ADR, and MP, although the timing of the hematopoietic recovery was not affected by MP, the overshoot of the [3H]deoxythymidine labelin index on Days 3 and 4 was abolished. Proliferative recovery in the tumor was delayed until after cessation of MP treatments. Cell kinetic changes in the tumor after CP, ADR, and MP were used to design effective sequential chemotherapy which obviated the hematopoietic toxicity associated with sequential therapy designed from cell kinetic changes after CP and ADR alone.
Cancer Res 1979 Oct
PMID:Effect of methylprednisolone on the cell kinetic response of C3H/HeJ mammary tumors to cyclophosphamide and adriamycin. 47 17

Findings from this study using a transplantable C3H mammary tumor failed to indicate interaction relative to growth parameters between two foci present in the same host. Whether they were growing alone or in the presence of a second focus, tumor growth rates were similar until the combined mass of multiple tumors approached that which was incompatible with survival. Only then was a difference in growth observed. Cytokinetic parameters, i.e., labeling index, primer-dependent DNA polymerase index or growth fraction, DNA synthesis time, tumor doubling time, and cell cycle time, were also similar whether tumors grew alone or in the presence of a second focus. Following removal of a tumor, changes were observed within 24 hr in the kinetics of the residual focus. There was an increase in labeling index (duration approximately equal to 10 days) and primer-dependent DNA polymerase index with a decrease in the tumor doubling time. Minimal change was noted in DNA synthesis time and cell cycle time. The kinetic changes observed were reflected in a measureable increase in tumor size approximately equal to a week following tumor removal. Absence of an alteration in DNA synthesis time and cell cycle time indicates that the increase in tumor growth was probably due to a conversion of noncycling cells in G0 phase into proliferation. Relationship of the findings to the use of adjuvant chemotherapy is considered.
Cancer Res 1979 Oct
PMID:Effect of surgical removal on the growth and kinetics of residual tumor. 47 22

Chemically synthesized beta-2'-deoxy-6-thioguanosine 5'-triphosphate, a putative active form of beta-2'-deoxy-6-thioguanosine, was used efficiently as a substrate for DNA synthesis catalyzed by DNA polymerase alpha from calf thymus. The deoxythioguanylate was incorporated into DNA by replacing deoxyguanylate and supported the further elongation of DNA chains on activated calf thymus DNA. In contrast, DNA polymerase beta used beta-2'-deoxy-6-thioguanosine 5'-triphosphate at a much lower rate. The reaction product of DNA polymerase alpha, i.e., 6-thioguanine-containing DNA, adsorbed specifically to the organomercurial agarose column, and showed a peak of UV absorption at 342 nm, which is characteristic of thioguanine.
Cancer Res 1979 Oct
PMID:Utilization of 2'-deoxy-6-thioguanosine 5'-triphosphate in DNA synthesis in vitro by DNA polymerase alpha from calf thymus. 47 32

Continuous exposure to inhibitory concentrations of methotrexate produces distinct rates of steady-state growth of murine leukemia L1210 and human leukemia CCRF-CEM cells in culture. Addition of thymidine to the medium produces reversal (6 to 40%) of this steady-state growth rate inhibition. This study utilized combinations of methotrexate and thymidine for an evaluation of the accompanying relationship between steady-state growth rate and changes in the ribo- and deoxyribonucleoside triphosphate pools. In L1210 cells exposed to methotrexate alone, the deoxythymidine 5'-phosphate (dTTP) pools decreased, whereas deoxyadenosine 5'-triphosphate, deoxyguanosine 5'-triphosphate, and deoxycytidine 5'-triphosphate (dCTP) remained relatively constant up to 70% inhibition of growth rate, with dCTP at a constant 112% of controls. The corresponding ribonucleoside triphosphates decreased only slightly. With the combination of methotrexate and thymidine resulting in up to 40% inhibition of growth rate, there was also a decrease in the dTTP pool while the other deoxyribonucleoside triphosphates remained relatively constant, and the corresponding ribonucleoside triphosphates again decreased only slightly. The dCTP pool was reduced to a constant 42% of control comparable to that produced by thymidine alone. With greater than 40% (with thymidine) or 70% (without thymidine) inhibition of growth rate, all pools decreased, but only dTTP was substantially reduced in proportion to the growth rate inhibition caused by methotrexate. The dTTP pool became depleted in spite of the presence of exogenous thymidine. Evaluation of CCRF-CEM cells indicated that inhibition of growth rate and nucleotide pool perturbations by methotrexate were similar to those observed in L1210 cells. However, in the presence of thymidine, inhibition of growth rate appeared related to decreased pools of dCTP, deoxyadenosine 5'-triphosphate, and deoxyguanosine 5'-triphosphate, rather than dTTP as was observed for L1210 cells. Hence, mammalian cells were capable of responding in a differential fashion to pharmacological perturbations, and this capacity may play a role in determining therapeutic selectivity. Since the ribonucleoside triphosphate decreases were slight and relatively uniform during methotrexate-induced perturbations, the deoxyribonucleoside triphosphate pools appear to be more directly related to inhibition of growth rate. The results are consistent with the concept that slight imbalances in the deoxyribonucleoside triphosphate pools dramatically inhibit DNA synthesis, as mediated through their interaction with DNA polymerase.
Cancer Res 1979 Sep
PMID:Evaluation of ribonucleoside and deoxyribonucleoside triphosphate pools in cultured leukemia cells during exposure to methotrexate or methotrexate plus thymidine. 47 79

A regulatory protein for DNA polymerase alpha, responsive to noncomplementary deoxyribonucleoside triphosphates, has been isolated from calf thymus. The regulatory protein was separated from DNA polymerase alpha using Affi-Gel Blue and gel filtration. The regulatory protein had a molecular weight of approximately 70,000 as determined by gel filtration, and its activity was nondialyzable, heat labile, and abolished by pronase treatment. In the presence of regulatory protein, DNA polymerase alpha activity, measured by using polydeoxyadenylate-oligodeoxythymidylate as template primer, was inhibited by 2'-deoxyguanosine 5'-triphosphate in a parabolic-competitive fashion [Ki = 15 +/- 1 (S.E.) microM] and by 2'-deoxycytidine 5'-triphosphate in a linear-competitive manner (Ki = 162 +/- 23 microM). Neither the four natural ribonucleoside triphosphates nor 2'-deoxyadenosine 5'-triphosphate inhibited the DNA polymerase-regulatory protein system to any significant extent. The regulatory protein by itself had no effect on either DNA polymerase alpha activity or the Km for template primer. These results indicate that deoxyribonucleoside triphosphate pools may be involved in the regulation of cellular DNA synthesis through a direct effect on DNA polymerization.
Cancer Res 1979 Nov
PMID:Isolation of a DNA polymerase alpha-associated regulatory protein from calf thymus. 49 66

Two lines of the 6C3HED (Gardner lymphosarcoma), 6C3HED-LeP and 6C3HED-ADL, were studied. The former is exquisitely sensitive to 9-beta-D-arabinofuranosyladenine (ara-A) and the latter is resistant. Cytological examinations and strain specificity tests indicated that they are both 6C3HED. DNA synthesis in the sensitive line was found to be more sensitive to ara-A in whole-cell incubations than it was in the resistant line. In cell-free extracts, the DNA synthesis of the sensitive line showed greater inhibition by 9-beta-D-arabinofuranosyladenine 5'-triphosphate. Lower ability to form 9-beta-D-arabinofuranosyladenine 5'-triphosphate or to allow access to the intracellular space was eliminated as an explanation for the resistance. Cells from an ara-A-resistant human leukemia were tested, and the DNA synthesis of the cells, in either whole cells or cell-free extract, was unaffected by ara-A or 9-beta-D-arabinofuranosyladenine 5'-triphosphate, respectively. This suggests that resistance has emerged by reason of change in the DNA polymerase(s) and that the finding may be important in the clinical use of ara-A.
Cancer Res 1978 Aug
PMID:Resistance to 9-beta-D-arabinofuranosyladenine in murine tumor cells. 58 Sep 2

DNA polymerase activity was studied as a function of stage of tumor growth and correlated with DNA synthesis measured by 3H-TdR uptake. Considerable variations in DNA synthesis activity occur at different growth stages and following host death. DNA alpha-polymerase activity did vary with growth stage in the ascites tumor. However, it did not have a clear correlation with DNA synthesis or with tumor growth. No striking fall in DNA polymerase enzyme levels occurred as the ascites tumor reached stationary phase in contrast to reports in some cell culture systems. A decrease occurred with advanced tumor stage and after host death. DNA beta-polymerase activity did not change with tumor growth stage.
Cancer Biochem Biophys 1977
PMID:DNA polymerases during tumor growth. 61 18


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