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At least 19 recordsLinked to original sources
PubMed1978

[Sister chromatid exchanges under bromine incorporation into DNA cytosine nucleotides. II. Utilization of 3H-deoxycytidine as a DNA cytosine precursor].

The incorporation of 3H-deoxycytidine (3H-Cdr) in the presence of thymidine (Tdr) into cultured human blood lymphocytes has been studied. The analysis of the label in interphase nuclei as well as in chromosomes at metaphase was carried out. The labeling was much higher when 3H-Cdr (0.5 to 1.0 C/ml, 2--4 x 10(-5) mM) was added to the cultures simultaneously with Tdr (4 x 10(-1) mM). This observation is considered as an indication that in the presence of high doses of Tdr exogeneous Cdr is utilized to synthesize cytosine of DNA rather than thymidine. During the first hours after its addition, the bulk of 3H-Cdr is eliminated from the culture medium. At 12 hrs of the incubation, the medium seems to be free of the nucleoside as shown particularly from the single chromatid localization of the label in chromosomes of the second mitosis. The incorporation into lymphocytes of 3H-Tdr administered in the same dose under the same conditions was registered for the whole period of observation (24 hrs). The data obtained are discussed in relation to lymphocyte catabolism of exogeneous nucleosides.

Bromodeoxycytidine↗
PubMed1979

[Sister chromatid exchanges in bromine incorporation into DNA cytosine nucleotides. III. 5-bromodeoxycytidine as a DNA thymine precursor. The characteristics of the exchanges].

Cell movement through the mitotic cycle and sister chromatid exchanges (SCE) were studied in human blood lymphocytes cultured in the presence of 5-bromodeoxycytidine (BrdC, 0.05 mM) plus thymidine (dT 0.4, 0.8, and 1.0 mM). In controls, lymphocytes were cultivated in the presence of 5-bromodeoxyuridine (BrdU, 0.05 mM) and deoxycytidine (0.1 mM), or BrdC alone. All nucleosides were added to the cultures 28 hours prior to fixation and were maintained in the medium for 16 hours. As determined from percentage of metaphases of 1st to 3rd divisions, BrdC did not release from thymidine block. This fact leads us to conclude that BrdC in contrast to deoxycytidine does not serve as a cytosine precursor. No significant differences in the frequency of SCE and their distribution among chromosomes were found between cultures treated with BrdC and with BrdU.

Bromine↗
PubMed2006

DNA-directed assembly of polyanilines: modified cytosine nucleotides transfer sequence programmability to a conjoined polymer.

A series of polyaniline (PANI) oligomers was constructed from monomer units covalently linked to duplex DNA through N-(2-aminoethyl) groups bonded through cytosines. DNA oligomers containing the aniline monomers were treated with horseradish peroxidase (HRP) and H2O2 under conditions known to cause polymerization of aniline. No change in the absorption spectrum of the DNA was observed for samples containing fewer than four contiguous aniline groups. However, for oligomers containing four, five, or six aniline units, treatment with HRP and H2O2 led to the appearance of absorption features characteristic of the conducting "proton doped" emeraldine oxidation state of PANI. Molecular modeling shows that the DNA is distorted in the region of the PANI, but flanking regions of the DNA maintain their B-form structure. These findings provide a method to exploit the self-recognition, self-assembly, and sequence programmability of DNA for the formation of conducting polymers.

Aniline Compounds↗
PubMed1980

Enzymatic addition of modified cytosine nucleotides to DNA. Methacrylate polymerization by an azo pyrimidine.

An azo pyrimidine that induces the polymerization of 1-glyceryl methacrylate has been prepared. 1-Glyceryl methacrylate contains substituent glycol groups for binding heavy atoms for subsequent electron microscopic studies. Oxodation of 1-methyl N4-ureidocytosine (compound 1A) with N-bromosuccinimide produced 4-aminocarbonylazo-2-pyrimidinone (compound 2A). This orange compound shows a broad peak (lambda max = 349 nm) in its ultraviolet absorption spectrum. Mixing compound 2A with mildly acidic aqueous solutions of 1-glyceryl methacrylate (pH 3.6) resulted in polymerization of the methacrylate. Under these conditions, the ester 1-glyceryl methacrylate does not hydrolyze appreciably as judged by oxidation of the glycol groups with NaIO4 and spectrophotometric analysis of the HCHO liberated using Schiff's reagent. Attachment of azo nucleotides to the 3'-terminus of DNA was achieved in two steps. First, N4-ureidocytosine deoxynucleotides were enzymatically added to single strand DNA primers using calf thymus terminal deoxynucleotidyl transferase, Co2+, and N4-ureido-2'-deoxycytidine 5'-triphosphate (prepared by the HSO3--catalyzed transamination reaction of dCTP with semicarbazide). Second, these modified nucleotides were oxidized with N-bromosuccinimide to produce DNA that contained azo pyrimidine nucleotides at its 3'-end (azoDNA). Upon adding acid to the azoDNA, the azo nucleotides decomposed. If these nucleotides induce methacrylate polymerization upon decomposition as did compound 2A, it may be possible to mark the location of DNA termini in situ for electron microscopy by attaching heavy atoms to the poly(1-glyceryl methacrylate) formed. Such studies may elucidate the nature and location of the ends of the eukaryotic chromosomal DNA molecule in both chromosomes and interphase nuclei.

Acrylic Resins↗
PubMed1998

Structures of escherichia coli CMP kinase alone and in complex with CDP: a new fold of the nucleoside monophosphate binding domain and insights into cytosine nucleotide specificity.

BACKGROUND: . Nucleoside monophosphate kinases (NMP kinases) catalyze the reversible transfer of a phosphoryl group from a nucleoside triphosphate to a nucleoside monophosphate. Among them, cytidine monophosphate kinase from Escherichia coli has a striking particularity: it is specific for CMP, whereas in eukaryotes a unique UMP/CMP kinase phosphorylates both CMP and UMP with similar efficiency. RESULTS: . The crystal structure of the CMP kinase apoenzyme from E. coli was solved by single isomorphous replacement and refined at 1.75 A resolution. The structure of the enzyme in complex with CDP was determined at 2.0 A resolution. Like other NMP kinases, the protein contains a central parallel beta sheet, the strands of which are connected by alpha helices. The enzyme differs from other NMP kinases in the presence of a 40-residue insert situated in the NMP-binding (NMPbind) domain. This insert contains two domains: one comprising a three-stranded antiparallel beta sheet, the other comprising two alpha helices. CONCLUSIONS: . Two features of the CMP kinase from E. coli have no equivalent in other NMP kinases of known structure. Firstly, the large NMPbind insert undergoes a CDP-induced rearrangement: its beta-sheet domain moves away from the substrate, whereas its helical domain comes closer to it in a motion likely to improve the protection of the active site. Secondly, residues involved in CDP recognition are conserved in CMP kinases and have no counterpart in other NMP kinases. The structures presented here are the first of a new family of NMP kinases specific for CMP.

Amino Acid Sequence↗
PubMed1987

[Effect of D-galactosamine on nucleotides in the rat heart. Effects of cytidine and uridine administration].

The treatment of rats by galactosamine (2 mmol/kg i.p.), which dramatically alters the metabolism of pyrimidine nucleotides in the liver, has been used to investigate the dynamics of pyrimidine nucleotides in the rat heart. Six hours after administration of the drug, the UTP and UDPG myocardial contents were decreased by respectively 40 and 52% while the sum of uracil nucleotides was increased by 66% and that of cytosine nucleotides by 15%. When administered 5 h after galactosamine treatment, cytidine (750 nmol/rat i.v.) induced a further increase in cytosine nucleotides (46% above control value 1 h later) without however effect on uracil nucleotides. On the other hand, the administration of uridine (250 nmol/rat, i.v. 5 h after galactosamine), while restoring UTP, UDPG and the pool of uracil nucleotides, provoked a decrease in cytosine nucleotide level (-17%). In the absence of galactosamine treatment, the administration of uridine and cytidine did not induce changes in nucleotide levels despite a rise in blood cytidine concentration. All these observations support the hypothesis that: 1. the pathway for cytosine nucleotide synthesis predominant in the heart is that utilizing preformed exogenous cytidine and 2. this pathway is mainly controlled by the intracellular concentration of UTP rather than that of CTP.

Adenine Nucleotides↗
PubMed1992

Purification and characterization of cytoplasmic 5'(3')-nucleotidase from rabbit spleen: characteristic differences of the enzyme from the rat spleen nucleotidase.

1. A 5'(3')-nucleotidase, which preferably hydrolyzed 3'-dTMP and 3'-dUMP, was highly purified from rabbit spleen cytosol. 2. The enzyme also hydrolyzes 3'-UMP, 5'-dUMP and guanine nucleotides, but does not hydrolyze any adenine nucleotides or cytosine nucleotides. 3. The activity is dependent upon Mg2+, Co2+ or Mn2+; the addition of deoxyinosine stimulates the activity, and the pH optimum for the hydrolysis of 3'-dTMP is 7.0. 4. Although the catalytic properties of the enzyme are similar to the 5'(3')-nucleotidase from rat spleen, these nucleotidases differ in their molecular disposition. 5. The charge state of the rabbit enzyme is slightly basic, and the subunit M(r) is about 27 kDa, while the value of the rat enzyme is 26 kDa. 6. Immunochemical experiments with the use of antibodies against the purified nucleotidase indicate that enzymes from rabbit spleen and from rat spleen are composed of different polypeptides.

Animals↗
PubMed1995

[Vasoconstrictor effect of uridine triphosphate on pancreatic vascular bed].

Purinoceptors have been classified according to their sensitivity to structural analogues of purines. In addition to the well established and widely distributed P2 purinoceptor subtypes (P2X and P2Y), the existence of "pyrimidine" or "nucleotide" receptors was proposed, which are sensitive to the pyrimidine nucleotide, uridine triphosphate (UTP). Recently, this class of receptor has been included in the P2 purinoceptor classification as a P2U subtype. We have previously shown that pancreatic vascular resistance was modulated by the activation of P2Y and P2X purinoceptors, inducing vasodilation and vasoconstriction respectively. In this study, we investigated the effect of pyrimidine nucleotides on pancreatic vessels. The experiments were performed on isolated rat pancreas perfused at a constant pressure, which was selected to obtain a stable flow rate of 2.5 ml/min before drug administration; thus, any change in pancreatic vascular resistance resulted in a change in the flow rate. UTP induced a decrease in the flow rate at all concentrations tested, but the kinetics differed according to the concentration. The lowest concentration used (16.5 microM) induced a delayed, progressive and long lasting vasoconstriction. Ten times and one hundred times higher concentrations (165 and 1,650 microM) induced an immediate, more pronounced and also long lasting vasoconstriction. In contrast, the other pyrimidine nucleotide cytosine triphosphate (16.5 and 165 microM) did not significantly modify the pancreatic flow rate. This study suggests the presence of a P2U purinoceptor on rat pancreatic vessels; this P2U receptor differs from the P2X receptor since the activation of this latter elicits only a transient vasoconstriction.

Animals↗
PubMed1996

Sequences in the -35 region of Escherichia coli rpoS-dependent genes promote transcription by E sigma S.

sigma S is an alternate sigma factor which functions with RNA polymerase to activate transcription of genes that are involved in a number of stress responses, including stationary-phase survival and osmoprotection. The similarity of the sigma S protein to sigma D (Escherichia coli's major sigma factor) in the regions thought to recognize and bind promoter sequences suggests that sigma S- and sigma D-associated RNA polymerases recognize promoter DNA in a similar manner. However, no promoter recognition sequence for sigma S holoenzyme (E sigma S) has been identified. An apparent conservation of cytosine nucleotides was noted in the -35 region of several sigma S-dependent promoters. Site-directed mutagenesis and reporter gene fusions were used to investigate the importance of the -35 cytosine nucleotides for sigma S-dependent transcription. Substitution of cytosine nucleotides for thymidine at the -35 site of the sigma D-dependent proU promoter effectively abolished transcription by E sigma D but allowed E sigma S to direct transcription from the mutant promoter. Inclusion of the sigma D consensus -10 hexamer strengthened transcription by E sigma S, demonstrating that both E sigma D and E sigma S can recognize the same -10 sequences. Conversely, replacement of -35 site cytosine nucleotides with thymidine in the sigma S-dependent osmY promoter reduced transcription by E sigma S and increased transcription by E sigma D. Our data suggest that DNA sequences in the -35 region function as part of a discriminator mechanism to shift transcription between E sigma D and E sigma S.

Amino Acid Transport Systems↗
PubMed1996

A spectrophotometric study of the interaction of VO2+ with cytosine in nucleotides.

The interaction of VO2+ with cytidine-monophosphate, -diphosphate, and -triphosphate has been investigated at different pH values and metal-to-ligand ratios by differential UV-absorption spectroscopy. It is shown that at pH values between 3 and 5 and for metal-to-ligand ratios up to 0.5, the cytosine ring is involved in coordination. On the other hand, measurements performed at pH = 7 show the absence of this type of interaction. Some comments on the possible structural characteristics of the generated complexes are made on the basis of the known coordination behavior of cytosine. Similar spectroscopic measurements with the systems VO2+/PO(3-)4, VO2+/P2O(4-)7, and VO2+/D-ribose were also performed in order to complement the analysis of the experimental results.

Cytosine↗
PubMed1978

[Sister chromatid exchanges following incorporation of bromine into cytosine DNA nucleotides. I. Combined use of 5-bromdeoxycytidine and thymidine for the purpose of incorporating bromine into DNA cytosine].

In the cultured in vitro human blood lymphocytes treated with 5-bromodeoxycytidine (BrdC) plus thymidine (dT) in concentrations of 0.05 mM and 0.4 mM, respectively, metaphases of the second division, containing chromosomes with differentially stained sister chromatids appear after a 30 hours treatment, attaining 85 per cent at 36 hours. Under the treatment with BrdC or BrdU alone, the similar percentage of metaphases is observed at 28 hours. Similar results are obtained if, at 16--18 hours, the culture medium, containing BrdC plus dT is either replaced with a medium free of both the precursors, or supplied once more vith (0.05 mM) or dC(0.05 mM). The The observed slowing movement of cells through out the cell cycle, due to the treatment with BrdC plus dT, is explained by the inhibitory effect of dT on DNA synthesis which is manifested as BrdC catabolism. It is concluded that BrdC administered together with the cell cycle-slowing doses of thymidine is predominantly incorporated into cytosine of DNA.

Bromodeoxycytidine↗
PubMed1981

Changes in myocardial pyrimidine nucleotide levels following repeated injections of isoproterenol in rats.

Changes which might lead to the initiation of cardiac hypertrophy include possible variations in the dynamics of nucleotides. In the experiments reported in this paper, changes in the pool sizes of adenine, uracil and cytosine nucleotides were observed during the initial phase of cardiac overload. Repeated subcutaneous injections of isoproterenol (ISO) (5 mg . kg-1 body weight, s.c.) were performed so as to produce symmetric cardiomegaly in rats. Under these conditions, the dry weight of the heart, on the fifth day of dialy injections of ISO, had increased by 43% and the RNA concentration by 39%. There was no significant change in the DNA concentration. No further changes in weight or in DNA and RNA concentrations were recorded from the fifth to the tenth day of treatment. Changes in UTP and ATP were carefully monitored during the first days following ISO application. The levels of both nucleotides decreased sharply at first. The ATP level remained below the control value for at least 48 h while the UTP level was rapidly restored and a further increase occurred resulting in a maximal enlargement of 82% after the 12th h. At the same time, the uracil nucleotide pool and the cytosine nucleotide pool had increased by 76% and 101%, respectively, while the adenine nucleotide content of the myocardium remained 15% below control level. Repeated injections of ISO induced effects on ATP and UTP levels which were similar in direction but attenuated. The significance of an increase in the pyrimidine nucleotide pools in relation to nucleic acid synthesis is discussed.

Adenine Nucleotides↗