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)

We investigated, in a cloned hamster tracheal epithelial cell line HTE-B, the effects of inhibitors of DNA topoisomerase, novobiocin and nalidixic acid; of DNA polymerase, 1-beta-arabinofuranosylcytosine (ara-C) and 2',3'-dideoxythymidine; of ribonucleotide reductase, hydroxyurea; and of poly(ADP-ribose)synthetase, 3-aminobenzamide, upon the removal of benzo[a]pyrene adducted to DNA [B[a]P--DNA]. A substantial reduction in the rate of removal of the polycyclic hydrocarbon-adducts occurred when nalidixic acid was added to the HTE-B cells that had been previously incubated with B[a]P for 8 h. Novobiocin produced a similar, but less marked, effect. The rate of disappearance of the individual B[a]P--DNA adducts was measured by analysis of the h.p.l.c. profiles. Of the 5 major adducts observed under the h.p.l.c. conditions, 4 were reduced in control cells to 30% of the original levels by 24 h after removal of the B[a]P from the medium; adduct 5 was almost completely removed. In the presence of nalidixic acid, during the 24 h repair period, only the removal of adduct 5 was unimpaired; the removal of the other 4 adducts was significantly retarded. On the other hand, 3-aminobenzamide addition did not affect the rate of removal of B[a]P--DNA adducts from the HTE-B cells. We employed the combinations of ara-C and dideoxythymidine or ara-C and hydroxyurea to allow the accumulation of single strand breaks after incubation of the HTE-B cells with B[a]P. These breaks were assayed by alkaline elution analysis. Inclusion of these inhibitors during the 2 h after removal of the B[a]P from the medium resulted in the accumulation of 4-5 single strand breaks/10(10) daltons of HTE-B DNA. This compares with a minimum estimate of the number of adducts removed during this period of 3 adducts/10(7) daltons. This discrepancy may indicate that the majority of lesions are not repaired by a pathway sensitive to polymerase inhibitors. In the presence of 3-aminobenzamide, we routinely observed a 10% increase in the alkaline elution of the DNA obtained from B[a]P-treated cells (1-2 breaks/10(10) daltons). Our results indicate that an excision repair process may be involved in the removal of at least some of the B[a]P-induced damage to DNA. However, the repair of the multiple adducts is complex and may involve pathways other than classical excision repair.
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PMID:The influence of inhibitors on the repair of benzo[a]pyrene-damaged DNA in hamster tracheal epithelial cells. 632 Oct 50

Administration of hepatocarcinogens aflataxin B1 (AFB1) and N-nitrosodimethylamine (NDMA) to rats caused single-strand breaks in hepatic nuclear DNA. The damage was found to be maximum at 4 hours following AFB1 administration and at 2 hours following NDMA administration. These damages were repaired after 17 and 4 hours, respectively in cases of AFB1 and NDMA. The activity of poly(ADP-ribose)polymerase (PARP), an enzyme known to use single-strand breaks of DNA as cofactor, was observed to increase with increasing damage to DNA and decrease as and when this damage got repaired. DNA polymerase beta and DNA ligase activities were also seen to increase and decline in a way analogous to PARP. In contrast, DNA topoisomerase activity declined corresponding to an increase in PARP activity. These observations suggest a possible role of PARP in coordinating the activities of other enzymes involved in DNA repair. It is also envisaged that these parameters can be utilized to devise strategies to counteract the deleterious effects of chemical carcinogens.
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PMID:Activity of some nuclear enzymes associated with DNA repair following hepatocarcinogen administration to rats. 759 30

A model for eukaryotic DNA damage repair is proposed in which poly(ADP-ribose) polymerase(NAD+ ADP-ribosyl transferase, EC 2,4,2,30) plays an important role. In this model, poly(ADP-ribose) polymerase regulates transcription of genes that are induced by DNA-damaging agents. This transcriptional regulation results from poly(ADP-ribosyl)ation and inactivation of DNA sequence-specific regulatory proteins such as silencer element-binding proteins, thereby inducing transcription of DNA polymerase beta, which is a DNA repair enzyme in higher eukaryotes. Poly(ADP-ribose) polymerase has a number of similarities to RecA in Escherichia coli. Therefore, the genes related to DNA damage repair in higher eukaryotes are proposed to form a "poly(ADP-ribose) polymerase regulatory network" similar to the "SOS regulatory network" in E. coli.
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PMID:Speculations on the roles of ADP-ribosyl transferase based on analogies between RecA and poly(ADP-ribose) polymerase. 824 22

3T3-L1 preadipocytes have been shown to exhibit a transient increase in poly(ADP-ribose) polymerase (PARP) protein and activity, as well as an association of PARP with DNA polymerase alpha, within 12-24 h of exposure to inducers of differentiation, whereas 3T3-L1 cells expressing PARP antisense RNA showed no increase in PARP and are unable to complete the round of DNA replication required for differentiation into adipocytes. The role of PARP in differentiation-linked DNA replication has now been further clarified at both the cellular and enzymological levels. Flow cytometric analysis revealed that control 3T3-L1 cells progressed through one round of DNA replication prior to the onset of terminal differentiation, whereas cells expressing PARP antisense RNA were blocked at the G0/G1 phase of the cell cycle. Confocal microscope image analysis of control S phase cells demonstrated that PARP was localized within distinct intranuclear granular foci associated with DNA replication centers. On the basis of these results, purified replicative complexes from other cell types that had been characterized for their ability to catalyze viral DNA replication in vitro were analyzed for the presence of PARP. PARP exclusively copurified through a series of centrifugation and chromatography steps with core proteins of an 18-21S multiprotein replication complex (MRC) from human HeLa cells, as well as with the corresponding mouse MRC from FM3A cells. The MRC were shown to contain DNA polymerases alpha and delta, DNA primase, DNA helicase, DNA ligase, and topoisomerases I and II, as well as accessory proteins such as PCNA, RF-C, and RP-A. Finally, immunoblot analysis of MRCs from both cell types with monoclonal antibodies to poly (ADP-ribose) revealed the presence of approximately 15 poly(ADP-ribosyl)ated proteins, some of which were further confirmed to be DNA polymerase alpha, DNA topoisomerase I, and PCNA by immunoprecipitation experiments. These results suggest that PARP may play a regulatory role within the replicative apparatus as a molecular nick sensor controlling the progression of the replication fork or modulates component replicative enzymes or factors in the complex by directly associating with them or by catalyzing their poly(ADP-ribosyl)ation.
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PMID:The expression of poly(ADP-ribose) polymerase during differentiation-linked DNA replication reveals that it is a component of the multiprotein DNA replication complex. 879 42

Administration of hepatocarcinogens aflatoxin B1 and N-nitrosodimethylamine to rats caused single-strand breaks in nuclear DNA. Inclusion in the diet of rutin, a naturally occurring phenolic flavonoid glycoside, significantly reduced the appearance of such breaks. The protection against DNA damage was found to be reduction in the induction of repair enzymes polymerase, DNA polymerase beta and DNA ligase. Even associated with poly(ADP-ribose) a marginal dose of rutin was effective in this regard. Since DNA damage and inefficient repair are expected to initiate the process of carcinogenesis, modulation by rutin of these parameters emphasizes the protective role of this flavonoid against carcinogenesis induced by chemical carcinogens.
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PMID:Protective effect of rutin, a flavonol glycoside, on the carcinogen-induced DNA damage and repair enzymes in rats. 902 Sep 19

Computer analysis of a conserved domain, BRCT, first described at the carboxyl terminus of the breast cancer protein BRCA1, a p53 binding protein (53BP1), and the yeast cell cycle checkpoint protein RAD9 revealed a large superfamily of domains that occur predominantly in proteins involved in cell cycle checkpoint functions responsive to DNA damage. The BRCT domain consists of approximately 95 amino acid residues and occurs as a tandem repeat at the carboxyl terminus of numerous proteins, but has been observed also as a tandem repeat at the amino terminus or as a single copy. The BRCT superfamily presently includes approximately 40 nonorthologous proteins, namely, BRCA1, 53BP1, and RAD9; a protein family that consists of the fission yeast replication checkpoint protein Rad4, the oncoprotein ECT2, the DNA repair protein XRCC1, and yeast DNA polymerase subunit DPB11; DNA binding enzymes such as terminal deoxynucleotidyltransferases, deoxycytidyl transferase involved in DNA repair, and DNA-ligases III and IV; yeast multifunctional transcription factor RAP1; and several uncharacterized gene products. Another previously described domain that is shared by bacterial NAD-dependent DNA-ligases, the large subunits of eukaryotic replication factor C, and poly(ADP-ribose) polymerases appears to be a distinct version of the BRCT domain. The retinoblastoma protein (a universal tumor suppressor) and related proteins may contain a distant relative of the BRCT domain. Despite the functional diversity of all these proteins, participation in DNA damage-responsive checkpoints appears to be a unifying theme. Thus, the BRCT domain is likely to perform critical, yet uncharacterized, functions in the cell cycle control of organisms from bacteria to humans. The carboxyterminal BRCT domain of BRCA1 corresponds precisely to the recently identified minimal transcription activation domain of this protein, indicating one such function.
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PMID:A superfamily of conserved domains in DNA damage-responsive cell cycle checkpoint proteins. 903 68

The acridine derivative m-AMCA (methyl-N-[4-(9-acridinylamino)-2-methoxyphenyl]carbamate hydrochloride), a carbamate analogue of the topoisomerase II poison amsacrine, is distinguished by its high cytotoxicity against non-cycling tumour cells. We compared the response of cultured Lewis lung carcinoma cells to m-AMCA, amsacrine and the topoisomerase I poison camptothecin. The DNA polymerase inhibitor aphidicolin reversed the cytotoxicity of camptothecin fully, that of amsacrine partially, and that of m-AMCA minimally. The ability of m-AMCA to induce the enzyme poly(ADP-ribose)polymerase (PARP) was markedly lower than that of camptothecin or amsacrine. Cell cycle responses to m-AMCA and amsacrine were similar, with slowing of progress through S-phase and arrest in G2-phase. These cell cycle changes were also observed when plateau phase cultures were exposed to drug for 1 h, washed free of drug and cultured in fresh medium, with m-AMCA having a more pronounced effect than amsacrine and camptothecin having no effect. We also examined the role of p53 protein in the response using cultured human H460 cells. Both m-AMCA and amsacrine induced p53 protein expression in proliferating but not in non-proliferating H460 cells, and induced p21WAF1 regardless of proliferation status. Both induced G1-phase cell cycle arrest. It is suggested that two cytotoxicity mechanisms can be distinguished using these drugs. The first is specific for S-phase cells, is reversed by aphidicolin and induces PARP activity. The second is cell cycle non-specific, does not induce PARP and is unaffected by aphidicolin. Camptothecin activates only the first, m-AMCA primarily the second and amsacrine activates both.
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PMID:Cellular responses to methyl-N-[4-9-acridinylamino)-2-methoxyphenyl] carbamate hydrochloride, an analogue of amsacrine active against non-proliferating cells. 938 32

We previously identified and characterized the human leukemia (HL-60) cell DNA synthetic machinery as a multiprotein form of DNA polymerase, which was designated the DNA synthesome. This multiprotein replication complex contains DNA polymerases alpha and delta, primase, replication factor C, replication protein A, helicase, poly(ADPribose) polymerase, proliferating cell nuclear antigen, DNA ligase I, and topoisomerases I and II. Recently, the HeLa cell-derived DNA synthesome was identified as a discrete high molecular weight protein band in native polyacrylamide gels. Here, we report our findings regarding the change in the organizational status of the DNA synthesome when HL-60 cells undergo either terminal differentiation or temporary G1 growth arrest. We observed that the HL-60 cell DNA synthesome also migrates as a discrete high molecular weight protein band in nondenaturing polyacrylamide gels. This high molecular weight protein band was present in nuclei derived from both actively cycling cells and aphidicolin-arrested cells but was absent in TPA-induced terminally differentiated cells. We also found that DNA polymerase delta, replication factor C, and proliferating cell nuclear antigen are absent in cells that are induced to differentiate in response to 12-O-tetradecanoyl phorbol-13-acetate treatment but are present in actively cycling cells. The level of replication protein A in differentiated cells was similar to that of cycling cells, whereas the level of annexin I, a cytoskeleton protein, is higher in differentiated cells than it is in actively cycling cells. We conclude that the DNA synthesome remains integrated and inactive in temporarily growth-arrested cells but is disassembled in differentiated cells. Furthermore, we conclude that disassembly of the organized replication complex is a specific cellular event in the process of permanent cell cycle exit and that the process leading to disassembly may be regulated, in part, at the level of gene transcription.
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PMID:The biochemical status of the DNA synthesome can distinguish between permanent and temporary cell growth arrest. 941 24

We have previously described the isolation and characterization of an intact multiprotein complex for DNA replication, designated the DNA synthesome, from human breast cancer cells and biopsied human breast tumor tissue. The purified DNA synthesome was observed to fully support DNA replication in vitro. We had also proposed a model for the breast cell DNA synthesome, in which DNA polymerases alpha, delta, and epsilon, DNA primase, and replication factor C (RF-C) represent members of the core component, or tightly associated, proteins of the complex. This model was based on the observed fractionation, chromatographic, and sedimentation profiles for these proteins. We report here that poly(ADP-ribose)polymerase (PARP) and DNA ligase 1 are also members of the breast cell DNA synthesome core component. More importantly, in this report we present the results of coimmunoprecipitation studies that were designed to map the protein-protein interactions between several members of the core component of the DNA synthesome. Consistent with our proposed model for the breast cell DNA synthesome, our data indicate that DNA polymerases alpha and delta, DNA primase, RF-C, as well as proliferating cell nuclear antigen (PCNA), tightly associate with each other in the complex, whereas DNA polymerase epsilon, PARP, and several other components were found to interact with the synthesome via a direct contact with only PCNA or DNA polymerase alpha. The association of PARP with the synthesome core suggests that this protein may serve a regulatory function in the complex. Also, the coimmunoprecipitation studies suggest that the three DNA polymerases alpha, delta, and epsilon all participate in the replication of breast cell DNA. To our knowledge this is the first report ever to describe the close physical association of polypeptides constituting the intact human breast cell DNA replication apparatus.
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PMID:Mapping specific protein-protein interactions within the core component of the breast cell DNA synthesome. 956 11

Recent findings have demonstrated that terminally differentiated adult ventricular myocytes are capable of repairing DNA that has been damaged by exposure to oxygen free radicals. Despite the potential importance of DNA repair in cells that may survive many decades after injury, little is known about the mechanisms or regulation of repair. Since tobacco use has a well-defined role in the epidemiology and pathophysiology of heart disease, we tested the effects of nicotine on repair of free radical damaged plasmids by whole-cell protein extracts from adult myocytes. Exposure to a concentration of 25 microM nicotine increased incorporation of (32P)dCTP into damaged plasmids by 16%, and 50 or 100 microM nicotine increased incorporation by 32%. Nicotine did not alter the rate or amount of poly (ADP-ribose) on the major protein acceptor of molecular weight 113-116 kDa. Inhibition of DNA polymerase activity with pyridoxal 5'-phosphate revealed greater plasmid degradation in the presence of nicotine. We conclude that nicotine enhances DNA degradation and the increased repair is a consequence of this greater degradation.
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PMID:The effect of nicotine on DNA repair in adult myocytes. 973 35


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