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At least 199 records · Page 11Linked to original sources
PubMed1991

Activation of human monocyte-derived macrophages by interferon gamma is accompanied by increase of poly(ADP-ribose) polymerase activity.

We have investigated poly(ADP-ribosyl)ation processes in human monocyte-derived macrophages and the effect of the activating cytokine, interferon gamma (IFN-gamma) on these processes. IFN-gamma was shown to increase the activity of poly(ADP-ribose) polymerase in human macrophages. A 2-3-fold enhancement of poly(ADP-ribose) polymerase activity was observed after 3-4 h of incubation with IFN-gamma, whose effects were dose-dependent and maximal at 20-50 U/ml. Staining with anti-poly(ADP-ribose) antibodies and purification of ADP-ribosylated nuclear proteins by affinity chromatography over boronate agarose showed that enhancement of poly(ADP-ribose) polymerase activity by IFN-gamma was accompanied by accumulation of poly(ADP-ribose) polymers in nuclear proteins. The effects of IFN-gamma on poly(ADP-ribose) polymerase activity were not due to an enhanced accumulation of the message for the enzyme, indicating that the activation of the enzyme activity was due to post-transcriptional modifications. IFN-gamma was shown to induce DNA strand breaks in human macrophages. This phenomenon followed the same time-course and was evident with the same doses of IFN-gamma that increased poly(ADP-ribose) polymerase activity. Since poly(ADP-ribose) polymerase is known to require DNA nicks for its activity, the capability of IFN-gamma to induce DNA strand breaks can explain its effects on poly(ADP-ribosyl)ation processes.

DNA Damage↗
PubMed2006

ART2, a T cell surface mono-ADP-ribosyltransferase, generates extracellular poly(ADP-ribose).

NAD functions in multiple aspects of cellular metabolism and signaling through enzymes that covalently transfer ADP-ribose from NAD to acceptor proteins, thereby altering their function. NAD is a substrate for two enzyme families, mono-ADP-ribosyltransferases (mARTs) and poly(ADP-ribose) polymerases (PARPs), that covalently transfer an ADP-ribose monomer or polymer, respectively, to acceptor proteins. ART2, a mART, is a phenotypic marker of immunoregulatory cells found on the surface of T lymphocytes, including intestinal intraepithelial lymphocytes (IELs). We have shown that the auto-ADP-ribosylation of the ART2.2 allelic protein is multimeric. Our backbone structural alignment of ART2 (two alleles of the rat art2 gene have been reported, for simplicity, the ART2.2 protein investigated in this study will be referred to as ART2) and PARP suggested that multimeric auto-ADP-ribosylation of ART2 may represent an ADP-ribose polymer, rather than multiple sites of mono-ADP-ribosylation. To investigate this, we used highly purified recombinant ART2 and demonstrated that ART2 catalyzes the formation of an ADP-ribose polymer by sequencing gel and by HPLC and MS/MS mass spectrometry identification of PR-AMP, a breakdown product specific to poly(ADP-ribose). Furthermore, we identified the site of ADP-ribose polymer attachment on ART2 as Arg-185, an arginine in a crucial loop of its catalytic core. We found that endogenous ART2 on IELs undergoes multimeric auto-ADP-ribosylation more efficiently than ART2 on peripheral T cells, suggesting that these distinct lymphocyte populations differ in their ART2 surface topology. Furthermore, ART2.2 IELs are more resistant to NAD-induced cell death than ART2.1 IELs that do not have multimeric auto-ADP-ribosylation activity. The data suggest that capability of polymerizing ADP-ribose may not be unique to PARPs and that poly(ADP-ribosylation), an established nuclear activity, may occur extracellularly and modulate cell function.

ADP Ribose Transferases↗
PubMed1985

Poly(ADP-ribose) in the cellular response to DNA damage.

Poly(ADP-ribose) polymerase is a chromatin-bound enzyme which, on activation by DNA strand breaks, catalyzes the successive transfer of ADP-ribose units from NAD to nuclear proteins. Poly(ADP-ribose) synthesis is stimulated by DNA strand breaks, and the polymer may alter the structure and/or function of chromosomal proteins to facilitate the DNA repair process. Electronmicroscopic studies show that poly(ADP-ribose) unwinds the tightly packed nucleosomal structure of isolated chromatin. Recent studies also show that the presence of poly(ADP-ribose) enhances the activity of DNA ligase. This may increase the capacity of the cell to complete DNA repair. Inhibitors of poly(ADP-ribose) polymerase or deficiencies of the substrate, NAD, lead to retardation of the DNA repair process. When DNA strand breaks are extensive or when breaks fail to be repaired, the stimulus for activation of poly(ADP-ribose) persists and the activated enzyme is capable of totally consuming cellular pools of NAD. Depletion of NAD and consequent lowering of cellular ATP pools, due to activation of poly(ADP-ribose) polymerase, may account for rapid cell death before DNA repair takes place and before the genetic effects of DNA damage become manifest.

Benzamides↗
PubMed1996

Properties of poly(ADP-ribose) glycohydrolase purified from pig testis nuclei.

A poly(ADP-ribose) glycohydrolase was purified more than 5,000-fold to apparent homogeneity from pig testis nuclei with a yield of 16%. A protein band, whose molecular mass (Mr) was estimated to be 58,000, detected by SDS-polyacrylamide gel electrophoresis of the purified preparation, was shown to have glycohydrolase activity upon assay by the renaturation method. A native Mr of 51,000 was determined by gel permeation. This polypeptide is a basic protein with a pI value of 8.8. The mode of hydrolysis of poly(ADP-ribose) [(ADP-ribose)n] by this enzyme is exoglycosidic, yielding ADP-ribose as the final product. The Km value for (ADP-ribose)n (average chain length, n = 15) is 5.4 microM and the Vmax of its hydrolysis is 34.5 micromol x min(-1) x mg protein(-1). The optimum pH for enzyme activity is 7.2. Low concentrations (50 approximately 150 mM) of monovalent salts stimulate the enzyme activity. The poly(ADP-ribose) glycohydrolase present in pig testis nuclei has some properties different from either nuclear poly(ADP-ribose) glycohydrolase (type I) or cytoplasmic poly(ADP-ribose) glycohydrolase (type II), purified previously from several tissues including pig thymus, guinea pig liver, calf thymus, human erythrocytes, and placenta. These differences suggest the tissue specificity of poly(ADP-ribose) glycohydrolase.

Animals↗
PubMed1984

Spectrophotometric and radioenzymatic determination of ribose-5-phosphate.

The present work describes an assay which is highly specific for ribose-5-phosphate. The method is based on the following three-stage enzymatic conversion: (1) ribose 5-phosphate in equilibrium ribose 1-phosphate (phosphopentomutase); (2) ribose 1-phosphate + adenine in equilibrium adenosine + Pi (adenosine phosphorylase); (3) adenosine + H2O----inosine + NH3 (adenosine deaminase). Ribose 5-phosphate may be determined either directly following the change in absorbance at 265 nm associated with the conversion of adenine to inosine, or radioenzymatically by measuring the radioactivity of inosine formed from [8-14C]adenine, after chromatographic separation of the nucleoside on polyethyleneimine-cellulose. The spectrophotometric assay was used to follow ribose 5-phosphate formation and ribose 1-phosphate consumption catalyzed by phosphopentomutase. Further, the ability of alkaline phosphatase, 5'-nucleotidase and crude extract of Bacillus cereus cells to act on ribose 5-phosphate was tested. The radioenzymatic assay was proved useful in determining the levels of ribose 5-phosphate in rat tissues.

Animals↗
PubMed1998

Poly(ADP-ribose) polymerase, a potential target for drugs: Cellular regulatory role of the polymer and the polymerase protein mediated by catalytic and macromolecular colligative actions (Review).

The cellular coenzymatic role of NAD, being a pleiotropic cofactor for diverse cellular reactions, is extended to poly(ADP-ribose) and to the highly abundant nuclear protein, poly(ADP-ribose) polymerase, with special focus on the pharmacological action of ligands on the latter. The polymer is defined to possess a helical configuration. From direct analyses of the polymer under physiological conditions, it is concluded that the polymerase is dormant in normal tissues, but is activated under certain pathological conditions: malignancy, retroviral integrate containing cells, and in a variety of inflammatory states. The interaction of poly(ADP-ribose) polymerase ligands with the DNA component of the active poly (ADP-ribose) polymerase - DNA complex is shown. A major cellular function of the poly(ADP-ribose) polymerase protein is its binding capacity to a large number of nuclear proteins and DNA sites, an effect which is induced by drugs that inhibit the polymerase activity. The malignancy-reverting effect of poly(ADP-ribose) polymerase ligand drugs is illustrated in chemically and oncovirally transformed cancer cells. The poly(ADP-ribose) polymerase ligand-induced cessation of HIV replication is analyzed. Peroxynitrite-induced DNA damage-initiated pathological responses are shown to be inhibited by a specific poly(ADP-ribose) polymerase ligand. The irreversibly acting C-NO drugs oxidize asymmetric zinc fingers [poly(ADP-ribose) polymerase, HIV gag-precursor protein] and act as anti-cancer and anti-HIV agents, an effect that is regulated by cellular concentration of GSH.

Journal Article↗
PubMed1999

Cyclic ADP-ribose-mediated insulin secretion and Reg, regenerating gene.

Glucose is the primary stimulus of insulin secretion in pancreatic beta-cells of the islets of Langerhans. CD38 has both ADP-ribosyl cyclase, which catalyzes the formation of cyclic ADP-ribose from NAD+, and cyclic ADP-ribose hydrolase, which converts cyclic ADP-ribose to ADP-ribose. ATP, produced by glucose metabolism, inhibits the cyclic ADP-ribose hydrolase of CD38 and therefore causes cyclic ADP-ribose accumulation in beta-cells. Then, cyclic ADP-ribose acts as a second messenger for Ca2+ mobilization from the endoplasmic reticulum to secrete insulin. The mechanism of insulin secretion as described above is completely different from the conventional hypothesis in which Ca2+ influx from extracellular sources was assumed to play a role in insulin secretion by glucose. On the other hand, strategies for influencing the replication of islet beta-cells and the growth of the beta-cell mass may be more important for ameliorating diabetes. Reg, regenerating gene, is involved in the growth of the beta-cell mass, and Reg protein has been shown to increase the beta-cell mass in a 90% depancreatized diabetic rat model, thereby ameliorating the diabetes. CD38 is involved in the formation of cyclic ADP-ribose and is essential for the glucose sensitivity of beta-cells for insulin secretion. Therefore, CD38 gene and Reg gene will become targets for genetic engineering for diabetic beta-cells.

ADP-ribosyl Cyclase↗
PubMed2005

A novel fluorometric assay for ADP-ribose pyrophosphatase activity.

ADP-ribose pyrophosphatase (ADPRase) hydrolyzes ADP-ribose to ribose-5-phosphate and AMP. The ADPRase activity have been assessed by coupling the reaction to alkaline phosphatase and colorimetrically measuring the amount of inorganic phosphate released from AMP that is one of the products of ADPRase. Another but less sensitive colorimetric method has been employed: the reaction mixture was treated with charcoal to adsorb the adenine-containing compounds such as AMP and ADPR and subsequently remaining ribose-5-phosphate was measured colorimetrically. However, the measurement of inorganic phosphate cannot be feasible to assay ADPRase in phosphate-containing samples and the determination of ribose-5-phosphate also is less sensitive. Here we develop a fluorescent assay for ADPRase that utilizes 1, N(6)-etheno ADP-ribose, a fluorescent analogue of ADP-ribose. This method measures fluorescent 1, N(6)-etheno adenosine that is produced by coupling the hydrolysis of 1, N(6)-etheno ADP-ribose to dephosphorylation with alkaline phosphatase. The fluorometric assay is comparable in sensitivity and useful for ADPRase assay in phosphate-containing samples.

Adenosine Diphosphate↗
PubMed1998

Poly(ADP-ribose) modulates the properties of MARCKS proteins.

In mammalian cells, the formation of DNA strand breaks is accompanied by synthesis of poly(ADP-ribose). This nucleic acid-like homopolymer may modulate protein functions by covalent and/or noncovalent interactions. Here we show that poly(ADP-ribose) binds strongly to the proteins of the myristoylated alanine-rich C kinase substrate (MARCKS) family, MARCKS and MARCKS-related protein (also MacMARCKS or F52). MARCKS proteins are myristoylated proteins associated with membranes and the actin cytoskeleton. As targets for both protein kinase C (PKC) and calmodulin (CaM), MARCKS proteins are thought to mediate cross-talk between these two signal transduction pathways. Dot blot assays show that poly(ADP-ribose) binds to MARCKS proteins at the highly basic effector domain. Complex formation between MARCKS-related protein and CaM as well as phosphorylation of MARCKS-related protein by the catalytic subunit of PKC are strongly inhibited by equimolar amounts of poly(ADP-ribose), suggesting a high affinity of poly(ADP-ribose) for MARCKS-related protein. Binding of MARCKS-related protein to membranes is also inhibited by poly(ADP-ribose). Finally, poly(ADP-ribose) efficiently reverses the actin-filament bundling activity of a peptide corresponding to the effector domain and inhibits the formation of actin filaments in vitro. Our results suggest that MARCKS proteins and actin could be targets of the poly(ADP-ribose) DNA damage signal pathway.

Actins↗
PubMedDate not supplied

Metabotropic glutamate receptor activation and intracellular cyclic ADP-ribose release Ca2+ from the same store in cultured DRG neurones.

The whole cell patch clamp technique has been used to record Ca(2+)-activated cation and chloride conductances evoked by release of Ca2+ from intracellular stores of cultured neonatal dorsal root ganglion neurones. The aim of this study was to investigate metabotropic glutamate receptor (mGluR) mechanisms and evaluate a possible role for cyclic ADP-ribose as an intracellular signalling molecule. Glutamate and the metabotropic glutamate receptor agonist (1S, 3R)-ACPD-evoked transient depolarizations, Ca(2+)-activated inward currents and rises in intracellular Ca2+. The (1S, 3R)-ACPD-activated currents were insensitive to InsP3 signalling inhibitors, heparin and pentosan polysulphate. Intracellular application of ryanodine alone activated currents in this study and proved a difficult tool to use as a potential inhibitor of cyclic ADP-ribose-mediated responses. However, intracellular dantrolene did attenuate both (1S, 3R)-ACPD and cyclic ADP-ribose responses. Intracellular photo-release of cGMP and cyclic ADP-ribose mimicked the responses to mGluR receptor activation. Intracellular application of nicotinamide and W7 inhibited the responses to photo-released cGMP but did not prevent responses to mGluR activation. The cyclic ADP-ribose receptor antagonist 8-amino cyclic ADP-ribose attenuated responses to (1S, 3R)-ACPD, cGMP and cyclic ADP-ribose, but some Ca(2+)-activated inward currents were still observed in the presence of this antagonist. In conclusion, mGluR receptor activation, cGMP and cyclic ADP-ribose release Ca2+ from intracellular stores. Some evidence suggests that pharmacologically related pathways are involved.

Adenosine Diphosphate Ribose↗
PubMed2006

MNNG-induced cell death is controlled by interactions between PARP-1, poly(ADP-ribose) glycohydrolase, and XRCC1.

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.

Animals↗
PubMed1994

Endoglycosidic cleavage of branched polymers by poly(ADP-ribose) glycohydrolase.

Post-translational modification of nuclear proteins with poly(ADP-ribose) modules chromatin structure and may be required for DNA processing events such as replication, repair and transcription. The polymer-catabolizing enzyme, poly(ADP-ribose) glycohydrolase, is crucial for the regulation of polymer metabolism and the reversibility of the protein modification. Previous reports have shown that glycohydrolase digests poly(ADP-ribose) via an exoglycosidic mechanism progressing from the protein-distal end of the polymer. Using two independent approaches, we investigated the possibility that poly(ADP-ribose) glycohydrolase also engages in endoglycosidic cleavage of polymers. First, partial glycohydrolase digestion of protein-bound poly(ADP-ribose) led to the production of protein-free oligomers of ADP-ribose. Second, partial glycohydrolase digestion of a fixed number of protein-free poly(ADP-ribose) polymers resulted in a transient increase in the absolute number of polymers while polymer size continuously decreased. Furthermore, endoglycosidic activity produced linear polymers from branched polymers although branch points themselves were not a preferential target of cleavage. From these data, we propose a mechanism whereby poly(ADP-ribose) glycohydrolase degrades polymers in three distinct phases; (a) endoglycosidic cleavage, (b) endoglycosidic cleavage plus exoglycosidic, processive degradation, (c) exoglycosidic, distributive degradation.

Animals↗
PubMed2005

The influence of ATP on poly(ADP-ribose) metabolism.

ATP affects poly(ADP-ribose) metabolism at two distinct sites: it inhibits poly(ADP-ribose) polymerase-1 and activates the glycohydrolase directly. The inhibitory site of ATP on poly(ADP-ribose) polymerase-1 was identified by amino acid exchange mutation to be at the arginine 34 residue in the first Zn2+ finger. Mutation of 138 arginine residue of Zn2+ finger 2 had negligible influence on the inhibitory action of ATP, pinpointing arginine 34 of the first Zn2+ finger as the specific ATP site. The glycohydrolase protein was activated by ATP when the substrate was a long-chain ADP-ribose polymer, but not with a short-chain substrate. Isolated cell nuclei also responded to both inhibition of poly(ADP-ribose) polymerase by ATP and to poly(ADP-ribose) glycohydrolase activation by ATP, demonstrating that enzymological results can be extrapolated to cellular systems. The activation of poly(ADP-ribose) polymerase in nuclei by an alkylating drug was completely suppressed by ATP, demonstrating that the bioenergetic competence of cells can regulate the cytocidal action of DNA alkylating drugs. The potential significance of bioenergetic regulation of poly(ADP-ribose) metabolism is proposed.

Adenosine Triphosphate↗
PubMed1996

Expression of cyclic ADP-ribose-synthetizing CD38 molecule on human platelet membrane.

CD38 is a cell surface molecule widely used as a marker for immature and activated lymphocytes. It has been recently shown that CD38 displays three enzymatic activities: hydrolysis of NAD+ to ADP-ribose, synthesis of cyclic ADP-ribose from NAD+, and hydrolysis of cyclic ADP-ribose to ADP-ribose. Thus, CD38 plays a key role in the synthesis of cyclic ADP-ribose, a calcium-mobilizing compound. We investigate here the expression and cellular localization of CD38 in human platelets using a specific monoclonal antibody. Results showed that CD38 is expressed by human platelet membranes. Moreover, we show that platelet CD38 possesses NAD glycohydrolase, ADP-ribose cyclase, and cyclic ADP-ribose hydrolase activities. This finding indicates that the calcium-mobilizing agent cyclic ADP-ribose can be synthetized by human platelets and raises the question about the possible role of CD38 expression and enzymatic activities in the signal transduction pathways leading to platelet activation.

ADP-ribosyl Cyclase↗
PubMed1998

Ribose-enhanced synthesis of UTP, CTP, and GTP from parent nucleosides in cardiac myocytes.

The participation of ribose and its metabolites in some nucleoside salvage reactions is well established. Isolated adult rat cardiac myocytes were used as a model system to determine whether ribose acts as a general stimulant of salvage reactions in cardiac muscle, or whether only certain classes of nucleosides are affected by ribose. Myocytes were incubated with [3H]-adenosine, [3H]-cytidine, [3H]-guanosine, [3H]-thymidine, or [3H]-uridine for 30 or 60 min in the presence or absence of 5 mM ribose. The cells were extracted and the extracts assayed for [3H]-nucleoside and [3H]-nucleotide products. Salvage synthesis of cytosine, guanine and uracil nucleotides from the parent nucleosides was stimulated by ribose. Guanosine and uridine salvage appeared saturated at 50 microM external nucleoside (the dose response of cytidine salvage was not examined). Adenosine salvage was unaffected by ribose addition; the response to increasing external adenosine concentration was non-Michaelis-Menten, showing a peak of activity at 25 microM external nucleoside. Thymidine salvage was also unaffected by ribose, and was saturated at 50 microM external thymidine. These data suggest that adenosine and thymidine are metabolized to their respective nucleotide monophosphates by kinase activity. Cytidine, guanosine, and uridine salvage are stimulated by ribose, and must therefore be metabolized in part by nucleoside phosphorylase and phosphoribosyltransferase activity.

Animals↗
PubMed1993

Effects of therapeutic ribose levels on human lymphocyte proliferation in vitro.

Ribose has been used successfully in the treatment of ischemic heart disease and muscular enzyme deficiencies, and its administration also facilitates the diagnosis of coronary artery disease by influencing thallium-201 scintigraphy. Concerns about the safety of ribose therapy have been triggered by reports about inhibitory effects of ribose on cell proliferation in vitro. This study examines possible side effects of ribose on human lymphocytes. Unstimulated and mitogen-stimulated human lymphocytes were incubated with ribose concentrations associated with high-dose oral administration, i.e., 3.5 mM, and with two- (7 mM) and tenfold (35 mM) higher concentrations. Cell cultures with matching glucose concentrations served as controls. Incorporation of [3H]thymidine into cells was used to measure cell proliferation. No significant inhibition of human lymphocyte proliferation in vitro was observed in mitogen-stimulated cells. Unstimulated cultures showed significant inhibition only at 35 mM ribose. It is concluded that ribose plasma levels associated with high-dose oral administration do not inhibit human lymphocyte proliferation in vitro. No evidence was found that short-term ribose therapy is harmful to human lymphocytes.

Administration, Oral↗
PubMed1989

Metabolism of D-ribose administered continuously to healthy persons and to patients with myoadenylate deaminase deficiency.

D-ribose was administered orally or intravenously over at least 5 h to eight healthy volunteers and five patients with myoadenylate deaminase deficiency. Intravenous administration rates were 83, 167, and 222 mg/kg/h, which were well tolerated but oral administration of more than 200 mg/kg/h caused diarrhea. The average steady state serum ribose level ranged between 4.8 mg/100 ml (83 mg/kg/h, oral administration) and 81.7 mg/100 ml (222 mg/kg/h, intravenous administration). Serum glucose level decreased during ribose administration. The intestinal absorption rate of orally administered ribose was 87.8%-99.8% of the intake at doses up to 200 mg/kg/h without first pass effect. Urinary losses were 23% of the intravenously administered dose at 222 mg/kg/h. Ribose appeared to be excreted by glomerular filtration without active reabsorption; a renal threshold could not be demonstrated. The amount of ribose transported back from the tubular lumen depended on the serum ribose level. There was no difference in ribose turnover in healthy subjects and patients with MAD deficiency.

AMP Deaminase↗
PubMed1988

Cell cycle regulation of poly(ADP-ribose) synthetase in FR3T3 cells.

The properties of poly(ADP-ribose) synthetase were studied throughout the cell cycle progression of non-synchronized rat FR3T3 fibroblasts using an immunological and biochemical approach. Cells in the various phases of the cell cycle were sorted from an asynchronously growing population by using flow cytofluorometry. G1, S and G2 + M fractions were used for enzymatic assays in the presence of saturating concentrations of DNAase I for the analysis of total poly(ADP-ribose) synthetase; maximal enzyme activity was found in the G2 + M phase. Purified IgG, specific for the FR3T3 poly(ADP-ribose) synthetase were used for the labelling of endogenous synthetase in order to quantify the enzyme immunologically. Localization of nuclear immunofluorescence was observed and analysis of poly(ADP-ribose) synthetase content throughout the cell cycle were carried out using double fluorescent staining and cytofluorometry. Poly(ADP-ribose) synthetase content as measured immunologically was found to increase from G1 to S and G2 + M phases. Quiescent cells showed a lower content as measured immunologically of poly(ADP-ribose) synthetase than cells in the G1 phase. In exponentially growing cells, the ratio between enzyme activity of poly(ADP-ribose) synthetase over the amount of enzyme measured immunologically was found to be higher in the G2 + M phase. These results show that a cell-cycle specific event activates poly(ADP-ribose) synthetase in the G2 + M phase.

Animals↗