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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It was shown that chromatin isolated from the liver of adult rats is an effective cell-free system for studying DNA synthesis without using exogenous enzymes or DNA-template. Both replication synthesis initiated in vivo and unscheduled synthesis activated several fold after gamma-irradiation of isolated chromatin proceed in chromatin preparations. Unscheduled synthesis consists of template-dependent and template-independent synthesis. Template-dependent synthesis proceeds with a maximum rate in the presence of all four deoxynucleoside triphosphates (dNTP). Template-independent synthesis proceeds with an appearable maximum rate in the presence of one dNTP whose incorporation is inhibited by the addition of the rest dNTP. All three DNA synthesis in chromatin are ATP-dependent. Replication synthesis but not the unscheduled one is inhibited by actinomycin D and N-ethylmaleinimide. Repair inhibitor--0.01 M caffeine--suppresses the initiation of unscheduled synthesis, but does not influence its elongation. The incubation conditions of chromatin for unscheduled synthesis are optimalized as for temperature, pH, time of incubation, qualitative ionic composition of the medium, concentration of chromatin, ATP, dNTP, MgCl2, NaCl. Michaelis constants for TTP are equal to 1 mM for template-independent synthesis and 3 mM for template-dependent synthesis. At optimal conditions DNA of chromatin is lengthened by 8 X 10--3% as the result of template-dependent synthesis and by 1 X 10--3% as the result of template-independent. The transition from nuclei to chromatin as well as the purification of chromatin from nuclear membranes enhance the rate of unscheduled synthesis. On the other hand, addition of nucleoplasm or cell extract to the chromatin does not considerably influence the synthesis. So it is suggested that the enzymes of initiation and elongation of unscheduled DNA synthesis are concentrated in the chromatin. The plausible role of unscheduled synthesis in excision and postreplication repair of eukaryotic DNA is discussed.
Mol Biol (Mosk)
PMID:[Endogenous DNA synthesis in isolated chromatin]. 20 78

In E. coli strain 91P containing the mutator gene mutT-, caffeine, spermine and quinacrine, but not guanosine, act as antimutagens, reducing the frequencies of mutation from ara- leads to Ara.
Mol Gen Genet 1977 Sep 09
PMID:Antimutagens against mutT. 33 12

Postreplication repair and its inhibition by chloramphenicol and caffeine, as seen in alkaline sucrose gradients, were compared between a uv non-mutable strain uvrA- umuC- and normally mutable strains uvrA- recF- and uvrA- umu+rec+ of Escherichia coli K-12. The uvrA- umuC- strain performed postreplication repair as efficiently as the parental strain, while the repair in uvrA- recF- strain was dependent on UV dose. Both chloramphenicol and caffeine inhibited postreplication repair to an equal extent of about 25%, and 10%, respectively, in all three uvrA- strains of umuC36, recF- and umu+rec+. These observations suggest that postreplication repair is largely not responsible for UV mutagenesis.
Mol Gen Genet 1977 Nov 14
PMID:Effects of chloramphenicol and caffeine on postreplication repair in uvr A- umuC- und uvrA- recF- strains of Escherichia coli K-12. 34 Aug 97

Haploid and diploid wild type strains, and three classes of radiation-sensitive mutants of Saccharomyces cerevisiae were tested for enhancement of UV-inactivation by caffeine in growth medium. In addition, the sensitizing effect of caffeine was studied in a haploid and a diploid wild type strain after gamma-irradiation. The drug sensitized the UV-irradiated cells of all strains except those reported to be only slightly UV-sensitive but highly sensitive to ionizing radiation. After gamma-irradiation, no caffeine-enhancement of killing was observed in stationary phase cells of either the haploid or the diploid strain. However, log-phase cells of both strains were partially sensitized. The results of both sets of experiments suggested that caffeine interferes with a recombinational repair occurring in cells in S or G2 phase.
Mol Gen Genet 1977 Dec 14
PMID:Caffeine enhancement of radiation killing in different strains of Saccharomyces cerevisiae. 34 6

The mode and site of action of inhibitors of translation (initiation, elongation and termination of protein synthesis) in eukaryotic systems is reviewed. The isolation and characterization of a factor is described that binds Ac-Phe-tRNA to form a complex made up of binding factors, Ac-Phe-tRNA, and ribosome. The binding of Ac-Phe-tRNA probably occurs at the ribosomal site involved in the binding of the initiator substrate Met-tRNAF. The effect of inhibitors of the intitiation phase of protein synthesis on the nonenzymic Ac-Phe-tRNA binding to ribosomes is investigated. The two sites translocation model for translation in eukaryotic cells is presented and the effects of inhibitors on the various steps of protein synthesis are determined empirically. The site of action of inhibitors of peptide bond formation at the ribosomal peptidyl transferase center is elucidated. The action of inhibitors of translocation is sutdied in model cell-free systems from human cells. In addition, a number of methylxanthines are shown to enhance the elongation phase in polypeptide synthesis by stimulating the enzymic binding of aminoacyl-tRNA. The effect of caffeine, theophylline and its derivatives are shown to be fairly specific and dependent on the ribosome concentration. Aminophylline is shown to have a similar effect but also enhances aminoacyl-tRNA synthetase activity at low Mg++ concentrations, probably displacing the optimal concentration of Mg++ in the reaction. This second effect of aminophylline appears to be due to the ethylenediamine moiety of aminophylline since it is also observed in the presence of different polyamines but not in the presence of caffeine or theophylline.
Mol Cell Biochem 1976 Feb 16
PMID:Antibiotics and compounds affecting tanslation by eukaryotic ribosomes. Specific enhancement of aminoacyl-tRNA binding by methylaxnthines. 76 41

It is shown that caffeine antagonizes petite-induction with ethidium bromide under non-growth conditions when administered during or after mutagenic treatment. Caffeine itself is shown to be a petite-inducing agent when cells are grown in liquid glucose-complete-medium in the presence of the drug. A possible mode of action of caffeine in the ethidium bromide induced petite-mutagenesis is discussed.
Mol Gen Genet 1976 Jul 05
PMID:Effect of caffeine on the rho- -induction with ethidium bromide in Saccharomyces cerevisiae. 78 13

Treatment of growing cultures of Mycobacterium smegmatis with alkylating agents (methyl methanesulphonate, ethyl methanesulphonate, nitrogen mustard, or mitomycin C) or with ultraviolet light resulted in enhanced specific activities of a DNA polymerase and of an ATP-dependent deoxyribonuclease. Similar results had previously been obtained with hydroxyurea and with iron limitation. The three of these treatments which were tested (methyl methanesulphonate, mitomycin C and hydroxyurea) produced strand breaks or alkali-labile regions in the DNA of this organism. The increased enzyme activities could be prevented by simultaneous treatment with inhibitors of protein synthesis. In contrast, treatment of the cultures with intercalating agents (ethidium bromide, acridine orange, or proflavine), 5-fluorouracil, caffeine, or nalidixic acid, inhibited DNA synthesis without increasing the enzyme activities. These treatments did not produce strand breaks in the DNA of this organism. The results support the hypothesis that, in M. smegmatis, damage to DNA induces increased synthesis of enzymes associated with DNA repair.
Mol Gen Genet 1977 Feb 15
PMID:Increased DNA polymerase and ATP-dependent deoxyribonuclease activities following DNA damages in mycobacterium smegmatis. 84 85

1. The concentrations of plasma total and unconjugated bilirubin and of serum nonesterified fatty acids (NEFA) have been measured in two healthy subjects during fasts of up to 21 h. 2. Fasting was either continuous or interrupted by various procedures that altered the concentrations of NEFA and total bilirubin. 3. When NEFA concentrations were increased by the administration of noradrenaline, heparin or caffeine, bilirubin concentrations also rose. 4. When NEFA concentrations were lowered by insulin, bilirubin concentrations fell. 5. Meals of 3-138 kJ and more, taken during the fasting period, lowered total bilirubin and NEFA concentrations in both subjects, whereas the effects of smaller meals were less consistent. 6. These studies demonstrate a statistically significant correlation between total bilirubin and NEFA during uninterrupted fasting and an association between these variables under other experimental conditions. They suggest that the control of bilirubin concentrations in the blood is linked to lipid metabolism.
Clin Sci Mol Med 1977 Aug
PMID:The association between fasting hyperbilirubinaemia and serum non-esterified fatty acids in man. 89 Nov 4

The major part of the substantial gamma-resistance of wild-type Schizosaccharomyces pombe appears to be due to prereplicative recombinational repair mechanisms. The existence of a second "prereplicative G2" repair pathway, specific for gamma-induced damage, has now been deduced from studies of the effect of the repair inhibitor caffeine on gamma-irradiated G1 phase and G2 phase cells. only G2 cells are additionally inactivated on exposure to caffeine after gamma-irradiation. This shows that both known caffeine-sensitive gamma-repair processes (Gentner and wener, Molec. gen. Genet. 145, 1-5 [1976]) are dependent on the presence of a duplicated genome (2c) at the time of radiation exposure. Pathway I is the known "prereplicative G2" repair process (Fabre, Radiation Res. 56, 528-539 [1973]) which is involved in both UV- and gamma-repair, and which requires post-irradiation protein synthesis for activity. Pathway II represents a second distinct "prereplicative G2" repair mechanism; it differs from the first in that it is specific for repair of gamma-induced damage and appears to be constitutive.
Mol Gen Genet 1977 Jul 20
PMID:Evidence for second "prereplicative G2" repair mechanism, specific for gamma-induced damage, in wild-type Schizosaccharomyces pombe. 89 14

Inhibition of DNA repair by caffeine is manifested in Schizosaccharomyces pombe wild-type cells as an enhancement of UV- or gamma-irradiation-induced lethality. The progress of DNA repair processes involving one or more caffeine-sensitive steps may be conveniently followed by measuring the concomitant decrease of this lethal enhancement effect. By measuring, during post-irradiation incubation, the ability of cells to overcome susceptibility to repair inhibition by caffeine, we have determined the time course and requirements for repair in S. pombe. Recovery began immediately and took 150-200 min after gamma-irradiation and more than 500 min after UV-irradiation, for exposures which gave about 10% survival in the absence of caffeine. An incubation medium capable of supporting growth was required for caffeine-sensitive repair; no recovery occurred under liquid holding conditions. Survival curves after various recovery times indicated that a logarithmic phase cell population was homogeneous with respect to caffeine-sensitive repair of both UV- and gamma-ray-induced damage. Recovery from caffeine inhibition was compared for cells of different physiological states (logarithmic and stationary phase); although the importance of the physiological state was not the same for the two types of radiation, recovery was found to occur more rapidly in the more radiation-resistant state, in each case.
Mol Gen Genet 1975 Dec 30
PMID:Repair in Schizosaccharomyces pombe as measured by recovery from caffeine enhancement of radiation-induced lethality. 122 3


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