The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
Lars Thelander - One of the best experts on this subject based on the ideXlab platform.
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Ribonucleotide Reductase and mitochondrial DNA synthesis
Nature genetics, 2007Co-Authors: Lars ThelanderAbstract:The p53-inducible small subunit of Ribonucleotide Reductase (p53R2) was originally assumed to be involved in DNA repair. A new study finds mutations in the gene encoding p53R2 (RRM2B) in individuals with severe mitochondrial DNA depletion in muscle, demonstrating its central role in mitochondrial DNA synthesis.
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Yeast Sml1, a Protein Inhibitor of Ribonucleotide Reductase *
The Journal of biological chemistry, 1999Co-Authors: Andrei Chabes, Vladimir Domkin, Lars ThelanderAbstract:Abstract Ribonucleotide Reductase (RNR) catalyzes the reduction of Ribonucleotides to deoxyRibonucleotides; this step is rate-limiting in DNA precursor synthesis. A number of regulatory mechanisms ensure optimal deoxyRibonucleotide pools, which are essential for cell viability. The best studied mechanisms are transcriptional regulation of the RNR genes during the cell cycle and in the response to DNA damage, and the allosteric regulation of Ribonucleotide Reductase by nucleoside triphosphates. Recently, another mode of RNR regulation has been hypothesized in yeast. A novel protein, Sml1, was shown to bind to the Rnr1 protein of the yeast Ribonucleotide Reductase; this interaction was proposed to inhibit Ribonucleotide Reductase activity when DNA synthesis is not required (Zhao, X., Muller, E.G.D., and Rothstein, R. (1998) Mol. Cell 2, 329–340). Here, we use highly purified recombinant proteins to directly demonstrate that the Sml1 protein is a strong inhibitor of yeast RNR. The Sml1p specifically binds to the yeast Rnr1p in a 1:1 ratio with a dissociation constant of 0.4 μm. Interestingly, Sml1p also specifically binds to the mouse Ribonucleotide Reductase R1 protein. However, the inhibition observed in an in vitro mouse Ribonucleotide Reductase assay is less pronounced than the inhibition in yeast and probably occurs via a different mechanism.
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yeast sml1 a protein inhibitor of Ribonucleotide Reductase
Journal of Biological Chemistry, 1999Co-Authors: Andrei Chabes, Vladimir Domkin, Lars ThelanderAbstract:Abstract Ribonucleotide Reductase (RNR) catalyzes the reduction of Ribonucleotides to deoxyRibonucleotides; this step is rate-limiting in DNA precursor synthesis. A number of regulatory mechanisms ensure optimal deoxyRibonucleotide pools, which are essential for cell viability. The best studied mechanisms are transcriptional regulation of the RNR genes during the cell cycle and in the response to DNA damage, and the allosteric regulation of Ribonucleotide Reductase by nucleoside triphosphates. Recently, another mode of RNR regulation has been hypothesized in yeast. A novel protein, Sml1, was shown to bind to the Rnr1 protein of the yeast Ribonucleotide Reductase; this interaction was proposed to inhibit Ribonucleotide Reductase activity when DNA synthesis is not required (Zhao, X., Muller, E.G.D., and Rothstein, R. (1998) Mol. Cell 2, 329–340). Here, we use highly purified recombinant proteins to directly demonstrate that the Sml1 protein is a strong inhibitor of yeast RNR. The Sml1p specifically binds to the yeast Rnr1p in a 1:1 ratio with a dissociation constant of 0.4 μm. Interestingly, Sml1p also specifically binds to the mouse Ribonucleotide Reductase R1 protein. However, the inhibition observed in an in vitro mouse Ribonucleotide Reductase assay is less pronounced than the inhibition in yeast and probably occurs via a different mechanism.
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Rnr4p, a novel Ribonucleotide Reductase small-subunit protein.
Molecular and cellular biology, 1997Co-Authors: P J Wang, Lars Thelander, R Casagrande, X C Tian, Tim C. HuffakerAbstract:Ribonucleotide Reductases catalyze the formation of deoxyRibonucleotides by the reduction of the corresponding Ribonucleotides. Eukaryotic Ribonucleotide Reductases are a2b2 tetramers; each of the larger, a subunits possesses binding sites for substrate and allosteric effectors, and each of the smaller, b subunits contains a binuclear iron complex. The iron complex interacts with a specific tyrosine residue to form a tyrosyl free radical which is essential for activity. Previous work has identified two genes in the yeast Saccharomyces cerevisiae, RNR1 and RNR3, that encode a subunits and one gene, RNR2, that encodes a b subunit. Here we report the identification of a second gene from this yeast, RNR4, that encodes a protein with significant similarity to the b-subunit proteins. The phenotype of rnr4 mutants is consistent with that expected for a defect in Ribonucleotide Reductase; rnr4 mutants are supersensitive to the Ribonucleotide Reductase inhibitor hydroxyurea and display an S-phase arrest at their restrictive temperature. rnr4 mutant extracts are deficient in Ribonucleotide Reductase activity, and this deficiency can be remedied by the addition of exogenous Rnr4p. As is the case for the other RNR genes, RNR4 is induced by agents that damage DNA. However, Rnr4p lacks a number of sequence elements thought to be essential for iron binding, and mutation of the critical tyrosine residue does not affect Rnr4p function. These results suggest that Rnr4p is catalytically inactive but, nonetheless, does play a role in the Ribonucleotide Reductase complex. Ribonucleotide Reductases catalyze the formation of deoxyRibonucleotides by the reduction of the corresponding Ribonucleotides. Three classes of Ribonucleotide Reductases have been well characterized (24). Class I enzymes are found in all eukaryotes and some prokaryotes. The best-studied class I enzyme is the Escherichia coli Ribonucleotide Reductase (10, 30), an a2b2 tetramer that can be decomposed to two catalytically inactive homodimers, R1 (a2) and R2 (b2). Each of the larger a subunits possesses binding sites for substrate and allosteric effectors and also contains several redox-active cysteine residues. Each of the smaller b subunits contains a binuclear Fe(III) complex. The X-ray structure of E. coli R2 reveals that the iron ions are bridged by both an O 22 ion and the carboxyl group of a glutamate residue (22). Each iron is further liganded by two carboxyl oxygen atoms from aspartate or glutamate residues, a histidine Nd residue, and a water molecule. The recently solved structure of the mouse R2 protein indicates that the iron-binding center of eukaryotic proteins is similar to that of the E. coli protein (17). The iron complex interacts with a specific tyrosine residue to form a tyrosyl free radical which is essential for activity. The enzyme is inhibited by hydroxyurea, which specifically quenches the tyrosyl radical (19). Amino acid sequence alignments of the class 1 R2 proteins from different species identify 16 residues that are conserved in all of these proteins reported to date (7, 22). Most of these conserved residues are at the iron center or close to it. Previous work has identified two genes in the yeast Saccharomyces cerevisiae (RNR1 and RNR3) that encode R1 proteins (8) and one gene (RNR2) that encodes an R2 protein (7, 13). Here we report the identification of a second gene from this yeast, RNR4, that encodes a protein with significant similarity to the R2 proteins. However, Rnr4p lacks a number of sequence elements thought to be essential for enzymatic function. Our evidence suggests that Rnr4p is catalytically inactive but, nonetheless, does play a role in the Ribonucleotide Reductase complex.
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Inactivation of Ribonucleotide Reductase by nitric oxide.
Biochemical and biophysical research communications, 1991Co-Authors: Michel Lepoivre, Lars Thelander, Franck Fieschi, Jacques Covès, Marc FontecaveAbstract:Ribonucleotide Reductase has been demonstrated to be inhibited by NO synthase product(s). The experiments reported here show that nitric oxide generated from sodium nitroprusside, S-nitrosoglutathione and the sydnonimine SIN-1 inhibits Ribonucleotide Reductase activity present in cytosolic extracts of TA3 mammary tumor cells. Stable derivatives of these nitric oxide donors were either inactive or much less inhibitory. EPR experiments show that the tyrosyl radical of the small subunit of E. Coli or mammalian Ribonucleotide Reductase is efficiently scavenged by these NO donors.
Yusuke Nakamura - One of the best experts on this subject based on the ideXlab platform.
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a Ribonucleotide Reductase gene involved in a p53 dependent cell cycle checkpoint for dna damage
Nature, 2000Co-Authors: Hiroshi Tanaka, Seisuke Fukuda, Yoshiki Takei, Tatsuya Yamaguchi, Hirofumi Arakawa, Kenji Shiraishi, K. Matsui, Yusuke NakamuraAbstract:The p53 gene is frequently inactivated in human cancers. Here we have isolated a p53-inducible gene, p53R2, by using differential display to examine messenger RNAs in a cancer-derived human cell line carrying a highly regulated wild-type p53 expression system. p53R2 contains a p53-binding sequence in intron 1 and encodes a 351-amino-acid peptide with striking similarity to the Ribonucleotide Reductase small subunit (R2), which is important in DNA synthesis during cell division. Expression of p53R2, but not R2, was induced by ultraviolet and γ-irradiation and adriamycin treatment in a wild-type p53-dependent manner. Induction of p53R2 in p53-deficient cells caused G2/M arrest and prevented cells from death in response to adriamycin. Inhibition of endogenous p53R2 expression in cells that have an intact p53-dependent DNA damage checkpoint reduced Ribonucleotide Reductase activity, DNA repair and cell survival after exposure to various genotoxins. Our results indicate that p53R2 encodes a Ribonucleotide Reductase that is directly involved in the p53 checkpoint for repair of damaged DNA. The discovery of p53R2 clarifies a relationship between a Ribonucleotide Reductase activity involved in repair of damaged DNA and tumour suppression by p53.
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a Ribonucleotide Reductase gene involved in a p53 dependent cell cycle checkpoint for dna damage
Nature, 2000Co-Authors: Hiroshi Tanaka, Seisuke Fukuda, Yoshiki Takei, Tatsuya Yamaguchi, Hirofumi Arakawa, Kenji Shiraishi, K. Matsui, Yusuke NakamuraAbstract:The p53 gene is frequently inactivated in human cancers. Here we have isolated a p53-inducible gene, p53R2, by using differential display to examine messenger RNAs in a cancer-derived human cell line carrying a highly regulated wild-type p53 expression system. p53R2 contains a p53-binding sequence in intron 1 and encodes a 351-amino-acid peptide with striking similarity to the Ribonucleotide Reductase small subunit (R2), which is important in DNA synthesis during cell division. Expression of p53R2, but not R2, was induced by ultraviolet and γ-irradiation and adriamycin treatment in a wild-type p53-dependent manner. Induction of p53R2 in p53-deficient cells caused G2/M arrest and prevented cells from death in response to adriamycin. Inhibition of endogenous p53R2 expression in cells that have an intact p53-dependent DNA damage checkpoint reduced Ribonucleotide Reductase activity, DNA repair and cell survival after exposure to various genotoxins. Our results indicate that p53R2 encodes a Ribonucleotide Reductase that is directly involved in the p53 checkpoint for repair of damaged DNA. The discovery of p53R2 clarifies a relationship between a Ribonucleotide Reductase activity involved in repair of damaged DNA and tumour suppression by p53.
Qing Meng - One of the best experts on this subject based on the ideXlab platform.
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rare group i intron with insertion sequence element in a bacterial Ribonucleotide Reductase gene
Journal of Bacteriology, 2007Co-Authors: Qing Meng, Yi Zhang, Xiang-qin LiuAbstract:A rare group I intron in a cyanobacterial Ribonucleotide Reductase gene has been characterized. It contains a mobile insertion sequence element not required for RNA splicing. Ribonucleotide Reductase genes were found to be hot spots for all three types of self-splicing intervening sequences, including group I and II introns and inteins.
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Four Inteins and Three Group II Introns Encoded in a Bacterial Ribonucleotide Reductase Gene
The Journal of biological chemistry, 2003Co-Authors: Xiang-qin Liu, Jing Yang, Qing MengAbstract:Abstract A bacterial Ribonucleotide Reductase gene was found to encode four inteins and three group II introns in the oceanic N2-fixing cyanobacterium Trichodesmium erythraeum. The 13,650-bp Ribonucleotide Reductase gene is divided into eight extein- or exon-coding sequences that together encode a 768-amino acid mature Ribonucleotide Reductase protein, with 83% of the gene sequence encoding introns and inteins. The four inteins are encoded on the second half of the gene, and each has conserved sequence motifs for a protein-splicing domain and an endonuclease domain. These four inteins, together with known inteins, define five intein insertion sites in Ribonucleotide Reductase homologues. Two of the insertion sites are 10 amino acids apart and next to key catalytic residues of the enzyme. Protein-splicing activities of all four inteins were demonstrated in Escherichia coli. The four inteins coexist with three group II introns encoded on the first half of the same gene, which suggests a breakdown of the presumed barrier against intron insertion in this bacterial conserved protein-coding gene.
Marc Fontecave - One of the best experts on this subject based on the ideXlab platform.
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Activation of class III Ribonucleotide Reductase by thioredoxin.
The Journal of biological chemistry, 2001Co-Authors: Dominique Padovani, Etienne Mulliez, Marc FontecaveAbstract:Abstract Anaerobic Ribonucleotide Reductase provides facultative and obligate anaerobic microorganisms with the deoxyribonucleoside triphosphates used for DNA chain elongation and repair. In Escherichia coli, the dimeric α2 enzyme contains, in its active form, a glycyl radical essential for the reduction of the substrate. The introduction of the glycyl radical results from the reductive cleavage of S-adenosylmethionine catalyzed by the reduced (4Fe-4S) center of a small activating protein called β. This activation reaction has long been known to have an absolute requirement for dithiothreitol. Here, we report that thioredoxin, along with NADPH and NADPH:thioredoxin oxidoReductase, efficiently replaces dithiothreitol and reduces an unsuspected critical disulfide bond probably located on the C terminus of the α protein. Activation of reduced α protein does not require dithiothreitol or thioredoxin anymore, and activation rates are much faster than previously reported. Thus, in E. coli, thioredoxin has very different roles for class I Ribonucleotide Reductase where it is required for the substrate turnover and class III Ribonucleotide Reductase where it acts only for the activation of the enzyme.
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resveratrol a remarkable inhibitor of Ribonucleotide Reductase
FEBS Letters, 1998Co-Authors: Marc Fontecave, Michel Lepoivre, Eric Elleingand, Catherine Gerez, Olivier GuittetAbstract:Resveratrol, a natural phytoalexin found in grapes, is well known for its presumed role in the prevention of heart disease, associated with red wine consumption. We show here that it is a remarkable inhibitor of Ribonucleotide Reductase and DNA synthesis in mammalian cells, which might have further applications as an antiproliferative or a cancer chemopreventive agent in humans.
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8-Azidoadenosine and Ribonucleotide Reductase.
Biochemical and biophysical research communications, 1992Co-Authors: Béatrice Roy, Michel Lepoivre, Jean-luc Décout, Jean Lhomme, Marc FontecaveAbstract:Summary Inhibitors of Ribonucleotide Reductase are potential antiproliferative agents, since they deplete cells from DNA precursors. Substrate nucleoside analogues, carrying azido groups at the base moiety, are shown to have strong cytostatic properties, as measured by the inhibition of the incorporation of thymidine into DNA. One compound, 8-azidoadenosine, inhibits CDP reduction in cytosolic extracts from cancer cells. The corresponding diphosphate behaves as a substrate for Ribonucleotide Reductase while the triphosphate is an allosteric effector.
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Inactivation of Ribonucleotide Reductase by nitric oxide.
Biochemical and biophysical research communications, 1991Co-Authors: Michel Lepoivre, Lars Thelander, Franck Fieschi, Jacques Covès, Marc FontecaveAbstract:Ribonucleotide Reductase has been demonstrated to be inhibited by NO synthase product(s). The experiments reported here show that nitric oxide generated from sodium nitroprusside, S-nitrosoglutathione and the sydnonimine SIN-1 inhibits Ribonucleotide Reductase activity present in cytosolic extracts of TA3 mammary tumor cells. Stable derivatives of these nitric oxide donors were either inactive or much less inhibitory. EPR experiments show that the tyrosyl radical of the small subunit of E. Coli or mammalian Ribonucleotide Reductase is efficiently scavenged by these NO donors.
Hiroshi Tanaka - One of the best experts on this subject based on the ideXlab platform.
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a Ribonucleotide Reductase gene involved in a p53 dependent cell cycle checkpoint for dna damage
Nature, 2000Co-Authors: Hiroshi Tanaka, Seisuke Fukuda, Yoshiki Takei, Tatsuya Yamaguchi, Hirofumi Arakawa, Kenji Shiraishi, K. Matsui, Yusuke NakamuraAbstract:The p53 gene is frequently inactivated in human cancers. Here we have isolated a p53-inducible gene, p53R2, by using differential display to examine messenger RNAs in a cancer-derived human cell line carrying a highly regulated wild-type p53 expression system. p53R2 contains a p53-binding sequence in intron 1 and encodes a 351-amino-acid peptide with striking similarity to the Ribonucleotide Reductase small subunit (R2), which is important in DNA synthesis during cell division. Expression of p53R2, but not R2, was induced by ultraviolet and γ-irradiation and adriamycin treatment in a wild-type p53-dependent manner. Induction of p53R2 in p53-deficient cells caused G2/M arrest and prevented cells from death in response to adriamycin. Inhibition of endogenous p53R2 expression in cells that have an intact p53-dependent DNA damage checkpoint reduced Ribonucleotide Reductase activity, DNA repair and cell survival after exposure to various genotoxins. Our results indicate that p53R2 encodes a Ribonucleotide Reductase that is directly involved in the p53 checkpoint for repair of damaged DNA. The discovery of p53R2 clarifies a relationship between a Ribonucleotide Reductase activity involved in repair of damaged DNA and tumour suppression by p53.
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a Ribonucleotide Reductase gene involved in a p53 dependent cell cycle checkpoint for dna damage
Nature, 2000Co-Authors: Hiroshi Tanaka, Seisuke Fukuda, Yoshiki Takei, Tatsuya Yamaguchi, Hirofumi Arakawa, Kenji Shiraishi, K. Matsui, Yusuke NakamuraAbstract:The p53 gene is frequently inactivated in human cancers. Here we have isolated a p53-inducible gene, p53R2, by using differential display to examine messenger RNAs in a cancer-derived human cell line carrying a highly regulated wild-type p53 expression system. p53R2 contains a p53-binding sequence in intron 1 and encodes a 351-amino-acid peptide with striking similarity to the Ribonucleotide Reductase small subunit (R2), which is important in DNA synthesis during cell division. Expression of p53R2, but not R2, was induced by ultraviolet and γ-irradiation and adriamycin treatment in a wild-type p53-dependent manner. Induction of p53R2 in p53-deficient cells caused G2/M arrest and prevented cells from death in response to adriamycin. Inhibition of endogenous p53R2 expression in cells that have an intact p53-dependent DNA damage checkpoint reduced Ribonucleotide Reductase activity, DNA repair and cell survival after exposure to various genotoxins. Our results indicate that p53R2 encodes a Ribonucleotide Reductase that is directly involved in the p53 checkpoint for repair of damaged DNA. The discovery of p53R2 clarifies a relationship between a Ribonucleotide Reductase activity involved in repair of damaged DNA and tumour suppression by p53.
