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

---

Query: EC:2.4.2.30 (PARP)
13,611 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Poly(ADP-ribose)polymerase (PARP) is a DNA-binding protein that is activated upon induction of DNA breaks and supposed to play a role in DNA repair. To elucidate the effect of overexpression of PARP on the resistance of cells to mutagens, Chinese hamster ovary cells (both the line CHO-9 and the mutagen-hypersensitive derivative 27-1) were transfected with the human PARP cDNA along with pSV2neo. Treatment of the transfected cell population with a high dose of MNNG and selection with G418 gave rise to a significant increase of neo+ clones, as compared to the control transfection with pSV2neo + salmon sperm DNA. The frequency of survivors in these mass culture experiments was lower, however, than after transfection with the bacterial ada gene encoding the DNA repair protein O6-alkylguanine-DNA alkyltransferase. Thus transfection of PARP cDNA in CHO cells is only weakly effective in inducing alkylation resistance. This was confirmed by analyzing the mutagen resistance of individual PARP transfectant clones derived from CHO-9 and 27-1 cells that expressed increased levels of PARP mRNA, protein and PARP activity. These strains were slightly more resistant to the toxic effect of MMS and showed a reduced frequency of MMS-induced chromosomal aberrations. CHO-9-PARP transfectants also gained resistance to UV. From these data we conclude that, in CHO cells, PARP is limiting in handling critical lesions during the repair process and that increase of the amount of PARP protein can elicit some protection against genotoxic effects of mutagens.
...
PMID:Effect of transfection of human poly(ADP-ribose)polymerase in Chinese hamster cells on mutagen resistance. 751 39

We have studied the clonogenic survival response to X-rays and MNNG of V79 Chinese hamster cells and two derivative cell lines, ADPRT54 and ADPRT351, deficient in poly(ADP-ribose) polymerase (PARP) activity. Under conditions of exponential growth, both PARP-deficient cell lines are hypersensitive to X-rays and MNNG compared to their parental V79 cells. In contrast, under growth-arrested, confluent conditions, V79 and PARP-deficient cells become similarly sensitive to X-rays and MNNG suggesting that PARP may be involved in the repair of X-ray or MNNG-induced DNA damage in logarithmically growing cells but not in growth-arrested confluent cells. This suggestion, however, creates a dilemma as to how PARP can be involved in DNA repair in only selected growth phases while it is functionally active in all growth phases. To explain these paradoxical results and resolve this dilemma we propose a hypothesis based on the consistent observation that inhibition of PARP results in a significant increase in sister chromatid exchange (SCEs). Thus, we propose that PARP is a guardian of the genome that protects against DNA recombination. We have extended this theme to provide an explanation for our results and the studies done by many others.
...
PMID:Poly(ADP-ribose) polymerase: a guardian of the genome that facilitates DNA repair by protecting against DNA recombination. 1033 34

The concerted action of poly(ADP-ribose) polymerase (PARP) which synthesizes the poly(ADP-ribose) (pADPr) in response to DNA strand breaks and the catabolic enzyme poly(ADP-ribose) glycohydrolase (PARG) determine the level of polymer and the rate of its turnover. In the present study, we have shown that the quail myoblast cells have high levels of basal polymer as compared to the murine C3H10T1/2 fibroblasts. We have conducted this study to investigate how such differences influence polymer synthesis and its catabolism in the cells in response to DNA damage by alkylating agent. In quail myoblast cells, the presence of high MNNG concentration such as 200 microM for 30 min induced a marginal decrease of 15% in the NAD content. For C3H10T1/2 cell line, 64 microM MNNG provoked a depletion of NAD content by approximately 50%. The induction of the polymer synthesis in response to MNNG treatment was 6-fold higher in C3H10T1/2 cells than in quail myoblast cells notwithstanding the fact that 3-fold higher MNNG concentration was used for quail cells. The polymer synthesis thus induced in quail myoblast cells had a 4-5 fold longer half life than those induced in C3H10T1/2 cells. To account for the slow turnover of the polymer in the quail myoblast cells, we compared the activities of the polymer catabolizing enzyme (PARG) in the two cell types. The quail myoblast cells had about 25% less activity of PARG than the murine cells. This difference in activity is not sufficient to explain the large difference of the rate of catabolism between the two cell types implicating other cellular mechanisms in the regulation of pADPr turnover.
...
PMID:Poly(ADP-ribose) turnover in quail myoblast cells: relation between the polymer level and its catabolism by glycohydrolase. 1033 49

Poly(ADP-ribose) is a polymer (pADPr) that is synthesized by poly (ADP-ribose) polymerases in response to DNA damaging agents. For instance, chemical alkylating agents such as MNNG or physical stimulation of cells by gamma-rays are well known to induce pADPr synthesis. PARPs are members of a growing family of enzymes which includes PARP-1, PARP-2, S-PARP-1, tankyrase and V-PARP. The association of PARP-1 and PARP-2 in DNA damage signaling pathways has been characterized, but tankyrase and V-PARP seem to be independent of DNA repair mechanisms. Poly(ADP-ribosyl)ation leads to heterogenous chain lengths of up to 200 units (mers) in vitro. While most of these will be covalently bound to proteins, they may be released under alkaline conditions for analysis. Previous immunological methods such as immunoblots showed that about 60-70% of the 6-8 mers pADPr were lost during fixation and that the very short pADPr (2-5 mers) were very weakly bound to the membrane. Furthermore, detection of cellular pADPr using enzyme-linked immunosorbent assay (ELISA) revealed that some molecules of pADPr are also lost during fixation and washings. This phenomenon leads to underestimation of the short pADPr population in cells. Thus, evaluating which pADPr sizes are present in cells and tissues becomes critical. We report here the development of a new highly sensitive immunological method to detect synthesized pADPr sizes distribution in intact cells.
...
PMID:Analysis of ADP-ribose polymer sizes in intact cells. 1169 95

We addressed the analysis of the physical and functional association of proliferating cell nuclear antigen (PCNA), a protein involved in many DNA transactions, with poly(ADP-ribose) polymerase (PARP-1), an enzyme that plays a crucial role in DNA repair and interacts with many DNA replication/repair factors. We demonstrated that PARP-1 and PCNA co-immunoprecipitated both from the soluble and the DNA-bound fraction isolated from S-phase-synchronized HeLa cells. Immunoprecipitation experiments with purified proteins further confirmed a physical association between PARP-1 and PCNA. To investigate the effect of this association on PARP-1 activity, an assay based on the incorporation of radioactive NAD was performed. Conversely, the effect of PARP-1 on PCNA-dependent DNA synthesis was assessed by a DNA polymerase delta assay. A marked inhibition of both reactions was found. Unexpectedly, PARP-1 activity also decreased in the presence of p21waf1/cip1. By pull-down experiments, we provided the first evidence for an association between PARP-1 and p21, which involves the C-terminal part of p21 protein. This association was further demonstrated to occur also in vivo in MNNG (N-methyl-N'-nitro-N-nitrosoguanidine)-treated human fibroblasts. These observations suggest that PARP-1 and p21 could cooperate in regulating the functions of PCNA during DNA replication/repair.
...
PMID:Human proliferating cell nuclear antigen, poly(ADP-ribose) polymerase-1, and p21waf1/cip1. A dynamic exchange of partners. 1293 Aug 46

Poly(ADP-ribose) polymerases or PARPs are a family of NAD(+)-dependent enzymes that modify themselves and other substrate proteins with ADP-ribose polymers. The founding member PARP 1 is localized predominantly in the nucleus and is activated by binding to DNA lesions. Excessive PARP 1 activation following genotoxin treatment causes NAD(+) depletion and cell death, whereas pharmacological PARP 1 inhibition protects cells from genotoxicity. This study investigates whether cellular viability and NAD(+) metabolism are regulated by tankyrase-1, a PARP member localized predominantly in the cytosol. Using a tetracycline-sensitive promoter to regulate tankyrase-1 expression in Madin-Darby canine kidney (MDCK) cells, we found that a 40-fold induction of tankyrase-1 (from 1,500 to 60,000 copies per cell) lowers steady-state NAD(+) levels but does not affect basal cellular viability. Moreover, the induction confers protection against the oxidative agent H(2)O(2) and the alkylating agent MNNG, genotoxins that kill cells by activating PARP 1. The cytoprotective effect of tankyrase-1 is not due to enhanced scavenging of oxidants or altered expression of Mcl-1, an anti-apoptotic molecule previously shown to be down-regulated by tankyrase-1 in CHO cells. Instead, tankyrase-1 appears to protect cells by preventing genotoxins from activating PARP 1-mediated reactions such as PARP 1 automodification and NAD(+) consumption. Our findings therefore indicate a cytoprotective function of tankyrase-1 mediated through altered NAD(+) homeostasis and inhibition of PARP 1 function.
...
PMID:Tankyrase-1 overexpression reduces genotoxin-induced cell death by inhibiting PARP1. 1613

After genotoxic stress poly(ADP-ribose) polymerase-1 (PARP-1) can be hyperactivated, causing (ADP-ribosyl)ation of nuclear proteins (including itself), resulting in NAD(+) and ATP depletion and cell death. Mechanisms of PARP-1-mediated cell death and downstream proteolysis remain enigmatic. beta-lapachone (beta-lap) is the first chemotherapeutic agent to elicit a Ca(2+)-mediated cell death by PARP-1 hyperactivation at clinically relevant doses in cancer cells expressing elevated NAD(P)H:quinone oxidoreductase 1 (NQO1) levels. Beta-lap induces the generation of NQO1-dependent reactive oxygen species (ROS), DNA breaks, and triggers Ca(2+)-dependent gamma-H2AX formation and PARP-1 hyperactivation. Subsequent NAD(+) and ATP losses suppress DNA repair and cause cell death. Reduction of PARP-1 activity or Ca(2+) chelation protects cells. Interestingly, Ca(2+) chelation abrogates hydrogen peroxide (H(2)O(2)), but not N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced PARP-1 hyperactivation and cell death. Thus, Ca(2+) appears to be an important co-factor in PARP-1 hyperactivation after ROS-induced DNA damage, which alters cellular metabolism and DNA repair.
...
PMID:Calcium-dependent modulation of poly(ADP-ribose) polymerase-1 alters cellular metabolism and DNA repair. 1692 Jul 18

PARP-1 (poly(ADP-ribose) polymerases) modifies proteins with poly(ADP-ribose), which is an important signal for genomic stability. ADP-ribose polymers also mediate cell death and are degraded by poly(ADP-ribose) glycohydrolase (PARG). Here we show that the catalytic domain of PARG interacts with the automodification domain of PARP-1. Furthermore, PARG can directly down-regulate PARP-1 activity. PARG also interacts with XRCC1, a DNA repair factor that is recruited by DNA damage-activated PARP-1. We investigated the role of XRCC1 in cell death after treatment with supralethal doses of the alkylating agent MNNG. Only in XRCC1-proficient cells MNNG induced a considerable accumulation of poly(ADP-ribose). Similarly, extracts of XRCC1-deficient cells produced large ADP-ribose polymers if supplemented with XRCC1. Consequently, MNNG triggered in XRCC1-proficient cells the translocation of the apoptosis inducing factor from mitochondria to the nucleus followed by caspase-independent cell death. In XRCC1-deficient cells, the same MNNG treatment caused non-apoptotic cell death without accumulation of poly(ADP-ribose). Thus, XRCC1 seems to be involved in regulating a poly(ADP-ribose)-mediated apoptotic cell death.
...
PMID:MNNG-induced cell death is controlled by interactions between PARP-1, poly(ADP-ribose) glycohydrolase, and XRCC1. 1696 44

Poly(ADP-ribose)polymerase-1 (PARP-1) overactivation is a key event in neurodegeneration but the underlying molecular mechanisms wait to be unequivocally identified. Energy failure, transcriptional derangement and deadly nucleus-mitochondria cross-talk have been proposed as mechanisms responsible for PARP-1 neurotoxicity. In this study, we sought to determine how these mechanisms contributes to PARP-1-dependent neuronal death. We report that the PARP-1 activating agent methyl-nitrosoguanidine (MNNG) caused poly(ADP-ribosyl)ation-dependent death of pure mouse cortical neurons in culture. Upon PARP-1 hyperactivation, NAD and ATP storages only partially decreased, neurons rapidly acquired apoptotic morphology, apoptosis inducing factor and cytochrome c were released from mitochondria and caspase activation occurred. No evidence for p53 activation was found, lactate dehydrogenase release occurred only 18h later, and JNK kinase was constitutively activated and not affected by PARP-1 activation. The PARP-1 inhibitors 6-(5)H-phenanthridinone and N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylacetamide (PJ-34) prevented nucleotide depletion and cell death, whereas the transcription inhibitor actinomycin D did not affect PARP-1-dependent neurotoxicity. Together, our findings provide the first evidence that neither energy collapse nor transcriptional changes are involved in PARP-1-dependent apoptotic neuronal death, and support the existence of a poly(ADP-ribose)-mediated death signaling targeting mitochondria.
...
PMID:Neither energy collapse nor transcription underlie in vitro neurotoxicity of poly(ADP-ribose) polymerase hyper-activation. 1705

1-Methyl-3-nitro-1-nitrosoguanidine (MNNG) is a DNA alkylating agent. DNA alkylation by MNNG is known to trigger accelerated poly(ADP-ribose) metabolism. Various nitroso compounds release nitric oxide (NO). Therefore, we set out to investigate whether MNNG functions as NO donor and whether MNNG-derived NO or secondary NO metabolites such as peroxynitrite contribute to MNNG-induced cytotoxicity. MNNG in aqueous solutions resulted in time- and concentration-dependent NO release and nitrite/nitrate formation. Moreover, various proteins in MNNG-treated thymocytes were found to be nitrated, indicating that MNNG-derived NO may combine with cellular superoxide to form peroxynitrite, a nitrating agent. MNNG also caused DNA breakage and increased poly(ADP-ribose) polymerase activity and cytotoxicity in thymocytes. MNNG-induced DNA damage (measured by the comet assay) and thymocyte death (measured by propidium iodide uptake) was prevented by the PARP inhibitor PJ-34 and by glutathione (GSH) or N-acetylcysteine (NAC). The cytoprotection provided by PJ-34 against necrotic parameters was paralleled by increased outputs in apoptotic parameters (caspase activity, DNA laddering) indicating that PARP activation diverts apoptotic death toward necrosis. As MNNG-induced cytotoxicity showed many similarities to peroxynitrite-induced cell death, we tested whether peroxynitrite was responsible for at least part of the cytotoxicity induced by MNNG. Cell-permeable enzymic antioxidants (superoxide dismutase and catalase), the NO scavenger cPTIO or the peroxynitrite decomposition catalyst FP15 failed to inhibit MNNG-induced DNA breakage and cytotoxicity. In conclusion, MNNG induces tyrosine nitration in thymocytes. Furthermore, MNNG damages DNA by a radical mechanism that does not involve NO or peroxynitrite.
...
PMID:Protein tyrosine nitration and poly(ADP-ribose) polymerase activation in N-methyl-N-nitro-N-nitrosoguanidine-treated thymocytes: implication for cytotoxicity. 1742 24


1 2 Next >>

---