The effect of external deoxyribonucleosides on deoxyribonucleoside triphosphate concentrations in human lymphocytes.
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Animals↗
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Deoxyribonucleoside triphosphates in human cells: changes in disease and following exposure to drugs.
Deoxyribonucleic acid synthesis requires adequate cellular concentrations of the four deoxyribonucleoside triphosphates. Using a sensitive enzymic assay, we have measured the concentrations (pools) of these compounds in human bone marrow cells and in lymphocytes. The mean concentrations (pmol/10(6) cells) in normal human bone marrow cells were: deoxyadenosine triphosphate (dATP) 1.5; deoxyguanosine triphosphate (dGTP) 0.4; thymidine triphosphate (dTTP) 1.4 and deoxycytidine triphosphate (dCTP) 0.6; and in normal phytohaemagglutinin (PHA)-stimulated lymphocytes (72 h cultures); dATP 3.7; dGTP 1.9; dTTP 9.4 and dCTP 2.9. The deoxyribonucleoside triphosphate concentrations were increased approximately threefold in the nucleated marrow cells from patients with leukaemia and myeloproliferative diseases. PHA-stimulation of lymphocytes caused a marked increase of the deoxyribonucleoside triphosphate concentrations, particularly of dTTP, between 24 and 48 h of culture. In PHA-stimulated lymphocytes, the antifolate drugs methotrexate, pyrimethamine and trimethoprim, all produced a fall in dTTP and a rise in dATP concentrations within 1 h. These effects could be reversed by folinic acid. 5-Fluorouracil caused a fall in dTTP and in dCTP but no consistent changes in dATP; hydroxyurea caused a fall in dATP with a rise in dTTP. BCNU caused a significant fall in dATP and dCTP. Dibutyryl cyclic 3', 5' adenosine monophosphate and theophylline had no consistent effect on the deoxyribonucleoside triphosphate concentrations. 6-Mercaptopurine caused a fall in dATP and dGTP, the fall in dATP being marked after 4 h incubation. It is concluded that measurement of the deoxyribonucleoside triphosphates in human cells provides a new method of studying DNA synthesis in human disease states and of analysing the action of antimetabolite drugs on normal and diseased cells.
Adenosine Triphosphate↗
An isocratic high-pressure liquid chromatographic purification method for radioactively labeled deoxyribonucleoside triphosphates.
A method is described for the rapid purification of radioactively labeled deoxyribonucleoside triphosphates from their spontaneously emerging hydrolysis products deoxyribonucleoside diphosphate, deoxyribonucleoside monophosphate, and deoxyribonucleoside. The separations which are finished within 3 min or less are carried out on a 0.1 X 5 cm column filled with LiChrosorb-NH2, using isocratic elution with 0.025 M potassium phosphate, pH 6.8, in a high-pressure liquid chromatograph at room temperature and a flow rate of 30 ml-h-1 (flow velocity 63.7 cm-min-1).
Chromatography, High Pressure Liquid↗
Evaluation of ribonucleoside and deoxyribonucleoside triphosphate pools in cultured leukemia cells during exposure to methotrexate or methotrexate plus thymidine.
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.
Animals↗
Deoxyribonucleoside toxicity in adenosine deaminase and purine nucleoside phosphorylase deficiency: implications for the development of new immunosuppressive agents.
The immunodeficient state associated with adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) deficiency may result from the selective phosphorylation by thymus-derived lymphocytes of the ADA substrate deoxyadenosine and the PNP substrate deoxyguanosine, leading to the intracellular trapping of toxic deoxyribonucleoside triphosphates. Agents such as deoxycytidine might be able to favourably modify the immunodeficient state by inhibiting deoxyribonucleoside phosphorylation. Deficiencies of other nucleotide catabolic enzymes, if selectively expressed by lymphocytes, might also lead to immunodeficiency via nucleoside trapping in lymphoid tissues. Purine deoxyribonucleoside analogues, either alone or in combination with ADA inhibitors, may have value as lymphospecific antimetabolites.
Adenosine Deaminase↗
[Simple method of determining total deoxyribonucleosides in human urine].
A method for quantitative estimation of total deoxyribonucleosides in human urine is based on the preliminary purification of urine usina ion exchange resin Dowex 1X 8 in OH- form, subsequent treatment of urine with acetone-ethynol mixture and the quantitative estimation of deoxyribonucleosides content by a microbiologic method. Urine of healthy persons contained 95.4+/-12.7 microng of deoxyribonucleosides.
Bacteriological Techniques↗
Thymine 7-hydroxylase and pyrimidine deoxyribonucleoside 2' -hydroxylase activities in Rhodotorula glutinis.
Cell-free preparations from Rhodotorula glutinis catalyzed the conversion of deoxyribonucleosides to ribonucleosides in a pyrimidine deoxyribonucleoside 2' -hydroxylase reaction. The reaction occurred with only thymidine or deoxyuridine, of the common deoxyribonucleosides, without detachment of the deoxyribose moiety, at the nucleoside level. The same enzyme preparations catalyzed the conversion of thymine to 5-hydroxymethyluracil in a thymine 7-hydroxylase reaction. Requirements for molecular oxygen, alpha-ketoglutarate, Fe2+, and ascorbate indicated that the 2' -hydroxylase and 7-hydroxylase reactions are of the alpha-keto-acid dioxygenases class. The requirements for alpha-ketoglutarate and Fe2+ were very stringent. During the course of the 2' -hydroxylase and 7-hydroxylase reactions, alpha-ketoglutarate was decarboxylated to form succinate and CO2 so that the ratio of hydroxylated nucleoside or pyrimidine to CO2 was 1:1.5-Hydroxymethyluracil and 5-formyluracil also stimulated the decarboxylation of alpha-ketoglutarate and thus appeared to undergo 7-hydroxylase reactions.
Deoxyribonucleosides↗
Recovery from vitamin B-12-induced unbalanced growth. The shortened cell cycle and the deoxyribonucleoside triphosphate pools.
The deoxyribonucleoside triphosphate pools are undetectable in vitamin B-12-deficient cells of Euglena gracillis, but appear rapidly after the replenishment with the vitamin. They reach a maximum size that is about 6 times that of normal exponentially growing cells, but decrease to almost zero as the cells divide. The pools expand again during the post-replenishment shortened cell cycle. However, the expansion takes place during rather than before the resumption of DNA synthesis. The maximum sizes reached are still larger than in normal cells. By using the protein-synthesis inhibitor cycloheximide and determining the pool size, we found that vitamin-deficient cells apparently accumulate a large amount of ribonucleoside triphosphate reductase apoenzyme, which lacks the vitamin B12 coenzyme. We showed that the production of the deoxyribonucleoside triphosphates is not closely coupled to DNA synthesis under our experimental conditions, and that the concentration of the deoxyribonucleoside triphosphate pools per unit of DNA synthesized is almost constant for all stages of growth examined.
Cell Count↗
Deoxyribonucleoside triphosphate pools in herpes simplex type 1 infected cells.
Deoxyribonucleoside triphosphate pools were analysed in both exponentially growing and serum starved wild type BHK C13 cells and in a derivative of this cell line which lacks both thymidine kinase and deoxycytidine kinase activities, before and after infection with herpes simplex virus. Serum starved BHK cells had low levels of all four deoxyribonucleoside triphosphates. In exponentially growing cells all pools were expanded, the pool of dCTP being largest and dGTP the smallest. The dATP and dTTP pools were of intermediate sizes. In exponentially growing deoxypyrimidine kinase free cells the pools, with respect to level and distribution, were the same as those observed in wild type cells. After infection with herpes simplex virus there were marked changes in the levels of all deoxyribonucleoside triphosphate pools; the most predominant being a 25- to 50-fold expansion of dTTP pool. The pools of dCTP and dGTP also increased while the pool of dATP was very much reduced. These effects could be observed in both wild type and mutant cells.
Animals↗
The 7-methylbenz(a)anthracene deoxyribonucleoside products isolated from DNA after metabolism of the carcinogen by rat liver microsomes in the presence of DNA.
Metabolism of 7-methylbenz[a]anthracene (7MeBA) by 3-methylcholanthrene-induced rat liver microsomes in the presence of added native or denatured DNA resulted in covalent binding of the hydrocarbon to the nucleic acid. Enzymatic degradation and column chromatographic fractionation showed that the hydrocarbon-deoxyribonucleoside products were separable from the products similarly obtained from DNA having 7MeBA bound following treatment of mouse embryo cells in culture with this hydrocarbon. Comparison of the microsome catalysed hydrocarbon-deoxyribonucleoside products with those obtained by reaction with DNA of 7MeBA-5,6-oxide suggested that this K-region epoxide made a significant contribution to the liver microsome-induced DNA binding.
Animals↗
Purinogenic immunodeficiency diseases: selective toxicity of deoxyribonucleosides for T cells.
Deoxyadenosine at low concentrations and in the presence of an inhibitor of adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) is markedly toxic to lymphoblast cell lines of T cell origin but does not impair growth of B cell lines. Deoxyguanosine is also more toxic for T lymphoblasts. In the presence of deoxyadenosine or deoxyguanosine, elevation of the corresponding deoxyribonucleoside triphosphate (dATP or dGTP) occurs in T cell, but not in B cell, lines. The addition of deoxycytidine or dipyridamole results in lower dATP and dGTP levels and prevents deoxyribonucleoside toxicity. These findings provide a molecular basis for the immunodeficiency observed in individuals with several inborn errors of purine metabolism.
B-Lymphocytes↗
Biochemical basis for the enhanced toxicity of deoxyribonucleosides toward malignant human T cell lines.
Human malignant T cell lines have high levels of deoxyribonucleoside phosphorylating activity and low levels of deoxyribonucleotide dephosphorylating activity. When incubated with deoxyadenosine or thymidine, the malignant T cell lines rapidly accumulate toxic concentrations of dATP and dTTP, respectively. This unusual pattern of deoxyribonucleotide metabolism renders the malignant T cells especially vulnerable to the toxic effects of deoxyribonucleosides and related analogues.
B-Lymphocytes↗
Deoxyribonucleoside-requiring mutants of Bacillus subtilis.
A number of deoxyribonucleoside-requiring mutants (dns) of Bacillus subtilis were isolated and their growth characteristics and ribonucleotide reductase activities were compared with those of the wild type and of a dna mutant (tsA13). Both tsA13 and dns mutants required the presence of a mixture of deoxyribonucleosides for growth at 45 degrees C but not at 25 degrees C. All the mutant strains tested contained ribonucleotide reductase activity which showed heat sensitivity similar to that of the enzyme from a wild-type strain. The reductase in B. subtilis seemed to reduce ribonucleoside triphosphates in a similar manner to the enzyme in Lactobacillus leichmannii.
Bacillus subtilis↗
Highly stereoselective synthesis of (2'R)-[2'-2H]-deoxyribonucleosides and synthesis of their oligonucleotides.
Highly stereoselective synthesis of (2'R)-[2'-2H]-2'-deoxyribonucleosides (2'R:2'S = > 99:1) were accomplished by treating 2'-bromo-3',5'-O-TPDS-2'-deoxyribonucleosides with tributyltin deuteride at lower temperatures such as -60 degrees C in the presence of triethylborane. Moreover, synthesis of some oligodeoxyribonucleosides involving them will be described.
Boranes↗
The influence of calf thymus DNA and deoxyribonucleosides on the induction of different mutation types in drosophila.
The influence of exogenous DNA on the induction of mutations by X-rays was compared with the influence of an equimolar mixture of four deoxyribonucleosides. Pretreatment and posttreatment with calf thymus DNA did not influence the frequency of mutations at the specific loci dp, b, cn and bw as well as Minute mutations induced in Drosophila sperm by X-radiation. Pretreatment with the equimolar mixture of four deoxyribonucleosides increased the frequency of the Minutes, but it did not affect the frequency of mutations at the loci dp, b, cn, bw. Equimolar mixture of nucleosides alone induced a low frequency of Minute mutations in Drosophila sperm. DNA alone induced a low frequency of recessive lethals. These lethals arose as mosaics of small sectors of the gonads of F1 females and they were revealed as late as the F3 generation.
Animals↗
Studies on the penetration of mammalian cells by deoxyribonucleoside-5'-phosphates.
We have tested the ability of [5'-32P]-deoxyribonucleoside monophosphates (dNMPs) to penetrate living mouse fibroblast L cells and human HeLa cells. Under the conditions of our experiments, small numbers of apparently intact dNMP molecules appeared to penetrate into the interior of L cells and be incorporated into DNA. This incorporation was not due to mycoplasma contamination nor to extracellular hydrolysis of the dNMPs followed by resynthesis inside the cell. Under these same conditions, penetration of HeLa cells by intact dNMPs did not occur to a significant extent. However, HeLa cells were capable of hydrolyzing extracellular dNMPs to Pi and deoxyribonucleosides at a much faster rate than L cells. These experiments provide a starting point for attempts to specifically label the DNA in intact, living eukaryotic cells with [32P]-dNMPs.
Animals↗
[Studies on the thymidine-triphosphate synthesis in malignant tumors. I. Effects of thymidine on deoxyribonucleoside triphosphate pools and deoxyribonucleic acid synthesis (author's transl)].
Measurements of the deoxyribonucleoside triphosphate (dNTP) contents, the [14C] thymidine and deoxyuridine incorporation and the "key enzymes" of the thymidine triphosphate (dTTP) synthesis, thymidine kinase and ribonucleotide reductase, in diploid Ehrlich-ascites carcinoma, in Yoshida sarcoma-ascites cells and to a smaller extent in surgically removed malignant human tumours show 1. A distinctly increased dTTP content compared with the remaining dNTP is not a characteristic of tumour cells generally but a peculiarity of sarcoma and a sign of differentiation of a malignant tumour. 2. With simultaneous linear deoxyribonucleoside incorporation the dTTP content and the mix-proportion of [14C] dTTP to total dTTP in ascites tumour cells in short-term in-vitro incubation (120 min) remain constant. 3. Thymidine addition to the medium leads to a distinct rise of dTTP concentration even at a dosage of 3 X 10(-5) M. 4. The dNTP contents of ascites tumour cells are within the range of the endproduct-inhibiting concentrations of thymidine kinase and ribonucleotide reductase.
Animals↗
Deoxyribonucleoside triphosphate pools in synchronized human cells infected with herpes simplex virus types 1 and 2.
Deoxyribonucleoside triphosphate pools in uninfected and herpes simplex virus type 1 (HSV-1)- and HSV-2-infected KB cells were analyzed to determine whether ribonucleotide reductase functions in vivo in the presence and absence of thymidine (TdR). Previously we showed that HSV-2 replication was inhibited in KB cells blocked in their capacity to synthesize DNA by TdR. HSV-1 replication was not inhibited under these conditions. Both HSV-1 and HSV-2 induced an altered ribonucleotide reductase resistant to dTTP inhibition. Thus, the block to HSV-2 replication apparently was not at the level of reductase. However, the in vitro activity of the enzyme does not necessarily correspond to intracellular conditions. In TdR-blocked HSV-2-infected cells, we found that, while dTTP levels remained high, dCTP concentrations increased. In contrast, KB cells blocked by TdR showed increased dTTP but decreased dCTP levels. We conclude that the HSV-2 enzyme is functional in vivo and that TdR inhibits viral replication by a mechanism other than depletion of dCTP. Infection of KB cells with HSV-1 or HSV-2 altered both dATP and dGTP levels in the presence or absence of TdR. Inhibition of viral replication was not explained by changes in these pools. We suggest that, during infection, HSV-1 induces a virus function(s) not related to reductase which is resistant to TdR, whereas the corresponding HSV-2 function is sensitive. Our evidence shows that the TdR-sensitive function is not in the pathways leading to deoxyribonucleoside triphosphate and may occur at the level of DNA replication.
Adenosine Triphosphate↗