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Yaeta Endo - One of the best experts on this subject based on the ideXlab platform.
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rip and ralyase cleave the sarcin ricin domain a critical domain for ribosome function during senescence of wheat coleoptiles
Biochemical and Biophysical Research Communications, 2008Co-Authors: Tatsuya Sawasaki, Masahiro Nishihara, Yaeta EndoAbstract:Abstract Type-I ribosome-inactivating protein (RIP), which is found in many plants, catalyzes depurination of a specific adenine in the sarcin/ricin domain (SRD) of the large rRNA causing loss of ribosomal activity. Previously, we found a RNA Apurinic Site-specific lyase (RALyase) that catalytically cleaved the phosphodiester bond at the RIP-dependent depurination Site by β-elimination reaction. Here we show that both the RIP activity and RIP–RALyase-mediated cleavage of SRD in the cytoplasmic ribosome were induced at the late stage of senescence of wheat coleoptiles. Following this process, tissue death was observed. Furthermore, transgenic tobacco plants expressing glucocorticoid-induced RIP developed senescence-like phenotype. Our results suggest that ribosome inactivation due to the cleavage of SRD by the inducible RIP and constitutively expressed RALyase may be a unique plant system that mediates programmed cell death at the late senescent stage.
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a new class of enzyme acting on damaged ribosomes ribosomal rna Apurinic Site specific lyase found in wheat germ
The EMBO Journal, 1999Co-Authors: Tomio Ogasawara, Tatsuya Sawasaki, Ryo Morishita, Akihiko Ozawa, Kairat Madin, Yaeta EndoAbstract:A new enzyme, which we named ribosomal RNA Apurinic Site specific lyase (RALyase), is described. The protein was found in wheat embryos and has a molecular weight of 50 625 Da. The enzyme specifically cleaves the phosphodiester bond at the 3′ side of the Apurinic Site introduced by ribosome‐inactivating proteins into the sarcin/ricin domain of 28S rRNA. The 3′ and 5′ ends of wheat 28S rRNA at the cleavage Site are 5′‐GUACG‐α‐hydroxy‐α,β‐unsaturated aldehyde and pGAGGA‐3′, demonstrating that the enzyme catalyzes a β‐elimination reaction. The substrate specificity of the enzyme is extremely high: it acts only at the Apurinic Site in the sarcin/ricin domain of intact ribosomes, not on deproteinized rRNA or DNA containing Apurinic Sites. The amino acid sequences of five endopeptidase LysC‐liberated peptides from the purified enzyme were determined and used to obtain a cDNA sequence. The open reading frame encodes a protein of 456 amino acids, and a homology search revealed a related rice protein. Similar enzyme activities were also found in other plants that express ribosome‐inactivating proteins. We believe that RALyase is part of a complex self‐defense mechanism.
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Mechanism of ribosome RNA Apurinic Site specific lyase.
Nucleic Acids Symposium Series, 1999Co-Authors: Tatsuya Sawasaki, Ryo Morishita, Akihiko Ozawa, Tomio Ogasawara, Kairat Madin, Yaeta EndoAbstract:A new enzyme, which we named ribosome RNA Apurinic Site specific lyase (RALyase), has been characterized. The enzyme specifically cleaves a phosphodiester bond at the Apurinic Site in the sarcin/ricin domain of 28S rRNA in ribosomes. The cut ends of wheat 28S rRNA were determined as 5'---GUACG-alpha-hydroxy-alpha, beta-unsaturated aldehyde and pGAGGA---3' for the 3' fragment, demonstrating that the enzyme catalyzes the beta-elimination reaction.
E Francastel - One of the best experts on this subject based on the ideXlab platform.
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rat 7 8 dihydro 8 oxoguanine dna glycosylase substrate specificity kinetics and cleavage mechanism at an Apurinic Site
Nucleic Acids Research, 1998Co-Authors: M Prieto J Alamo, F Laval, Juan Jurado, E FrancastelAbstract:Reactive oxygen species produce different lesions in DNA. Among them, 7,8-dihydro-8-oxoguanine (8-oxoG) is one of the major oxidative products implicated in mutagenesis. This lesion is removed from damaged DNA by base excision repair, and genes coding for 8-oxoG-DNA glycosylases have been isolated from bacteria, yeast and human cells. We have isolated and characterized the cDNA encoding the rat 8-oxoG-DNA glycosylase (rOGG1). Expression of the cDNA in the fgp mutY Escherichia coli double mutant allowed the purification of the untagged rOGG1 protein. It excises 8-oxoG from DNA with a strong preference for duplex DNA containing 8-oxoG:C base pairs. rOGG1 also acts on formamidopyrimidine (FaPy) residues, and the K m values on 8-oxoG and FaPy residues are 18.8 and 9.7 nM, respectively. When acting on an oligonucleotide containing an 8-oxoG residue, rOGG1 shows a beta-lyase activity that nicks DNA 3' to the lesion. However, rOGG1 acts on a substrate containing an Apurinic Site by a beta-delta elimination reaction and proceeds through a Schiff base intermediate. Expression of rOGG1 in E.coli fpg mutY suppresses its spontaneous mutator phenotype.
Peter F Swann - One of the best experts on this subject based on the ideXlab platform.
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thymine dna glycosylase and g to a transition mutations at cpg Sites
Mutation Research-reviews in Mutation Research, 2000Co-Authors: Timothy R. Waters, Peter F SwannAbstract:Abstract About 23% of mutations in hereditary human diseases and 24% of mutations in p53 in human cancers are G to A transitions at Sites of cytosine methylation suggesting that these Sites are either foci for DNA damage, or foci for damage that is poorly repaired. Thymine produced at these Sites by the hydrolytic deamination of 5-methylcytosine is removed by thymine-DNA glycosylase. Thymine-DNA glycosylase will also remove 3, N 4 -ethenocytosine and uracil from DNA. The action of this enzyme is limited by its very low k cat and by tight binding to the Apurinic Site produced when the thymine is removed. These properties of the enzyme suggest that the inefficiency of the base excision repair pathway that it initiates may be the underlying cause of the prevalence of these mutations.
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human thymine dna glycosylase binds to Apurinic Sites in dna but is displaced by human Apurinic endonuclease 1
Journal of Biological Chemistry, 1999Co-Authors: Timothy R. Waters, Josef Jiricny, Paola Gallinari, Peter F SwannAbstract:Abstract In vitro, following the removal of thymine from a G·T mismatch, thymine DNA glycosylase binds tightly to the Apurinic Site it has formed. It can also bind to an Apurinic Site oppoSite S 6-methylthioguanine (SMeG) or oppoSite any of the remaining natural DNA bases. It will therefore bind to Apurinic Sites formed by spontaneous depurination, chemical attack, or other glycosylases. In the absence of magnesium, the rate of dissociation of the glycosylase from such complexes is so slow (k off 1.8 − 3.6 × 10−5 s−1; i.e. half-life between 5 and 10 h) that each molecule of glycosylase removes essentially only one molecule of thymine. In the presence of magnesium, the dissociation rates of the complexes with C·AP andSMeG·AP are increased more than 20-fold, allowing each thymine DNA glycosylase to remove more than one uracil or thymine from C·U and SMeG·T mismatches in DNA. In contrast, magnesium does not increase the dissociation of thymine DNA glycosylase from G·AP Sites sufficiently to allow it to remove more than one thymine from G·T mismatches. The bound thymine DNA glycosylase prevents human Apurinic endonuclease 1 (HAP1) cutting the Apurinic Site, so unless the glycosylase was displaced, the repair of Apurinic Sites would be very slow. However, HAP1 significantly increases the rate of dissociation of thymine DNA glycosylase from Apurinic Sites, presumably through direct interaction with the bound glycosylase. This effect is concentration-dependent and at the probable normal concentration of HAP1 in cells the dissociation would be fast. This interaction couples the first step in base excision repair, the glycosylase, to the second step, the Apurinic endonuclease. The other proteins involved in base excision repair, polymerase β, XRCC1, and DNA ligase III, do not affect the dissociation of thymine DNA glycosylase from the Apurinic Site.
M Prieto J Alamo - One of the best experts on this subject based on the ideXlab platform.
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rat 7 8 dihydro 8 oxoguanine dna glycosylase substrate specificity kinetics and cleavage mechanism at an Apurinic Site
Nucleic Acids Research, 1998Co-Authors: M Prieto J Alamo, F Laval, Juan Jurado, E FrancastelAbstract:Reactive oxygen species produce different lesions in DNA. Among them, 7,8-dihydro-8-oxoguanine (8-oxoG) is one of the major oxidative products implicated in mutagenesis. This lesion is removed from damaged DNA by base excision repair, and genes coding for 8-oxoG-DNA glycosylases have been isolated from bacteria, yeast and human cells. We have isolated and characterized the cDNA encoding the rat 8-oxoG-DNA glycosylase (rOGG1). Expression of the cDNA in the fgp mutY Escherichia coli double mutant allowed the purification of the untagged rOGG1 protein. It excises 8-oxoG from DNA with a strong preference for duplex DNA containing 8-oxoG:C base pairs. rOGG1 also acts on formamidopyrimidine (FaPy) residues, and the K m values on 8-oxoG and FaPy residues are 18.8 and 9.7 nM, respectively. When acting on an oligonucleotide containing an 8-oxoG residue, rOGG1 shows a beta-lyase activity that nicks DNA 3' to the lesion. However, rOGG1 acts on a substrate containing an Apurinic Site by a beta-delta elimination reaction and proceeds through a Schiff base intermediate. Expression of rOGG1 in E.coli fpg mutY suppresses its spontaneous mutator phenotype.
Timothy R. Waters - One of the best experts on this subject based on the ideXlab platform.
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thymine dna glycosylase and g to a transition mutations at cpg Sites
Mutation Research-reviews in Mutation Research, 2000Co-Authors: Timothy R. Waters, Peter F SwannAbstract:Abstract About 23% of mutations in hereditary human diseases and 24% of mutations in p53 in human cancers are G to A transitions at Sites of cytosine methylation suggesting that these Sites are either foci for DNA damage, or foci for damage that is poorly repaired. Thymine produced at these Sites by the hydrolytic deamination of 5-methylcytosine is removed by thymine-DNA glycosylase. Thymine-DNA glycosylase will also remove 3, N 4 -ethenocytosine and uracil from DNA. The action of this enzyme is limited by its very low k cat and by tight binding to the Apurinic Site produced when the thymine is removed. These properties of the enzyme suggest that the inefficiency of the base excision repair pathway that it initiates may be the underlying cause of the prevalence of these mutations.
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human thymine dna glycosylase binds to Apurinic Sites in dna but is displaced by human Apurinic endonuclease 1
Journal of Biological Chemistry, 1999Co-Authors: Timothy R. Waters, Josef Jiricny, Paola Gallinari, Peter F SwannAbstract:Abstract In vitro, following the removal of thymine from a G·T mismatch, thymine DNA glycosylase binds tightly to the Apurinic Site it has formed. It can also bind to an Apurinic Site oppoSite S 6-methylthioguanine (SMeG) or oppoSite any of the remaining natural DNA bases. It will therefore bind to Apurinic Sites formed by spontaneous depurination, chemical attack, or other glycosylases. In the absence of magnesium, the rate of dissociation of the glycosylase from such complexes is so slow (k off 1.8 − 3.6 × 10−5 s−1; i.e. half-life between 5 and 10 h) that each molecule of glycosylase removes essentially only one molecule of thymine. In the presence of magnesium, the dissociation rates of the complexes with C·AP andSMeG·AP are increased more than 20-fold, allowing each thymine DNA glycosylase to remove more than one uracil or thymine from C·U and SMeG·T mismatches in DNA. In contrast, magnesium does not increase the dissociation of thymine DNA glycosylase from G·AP Sites sufficiently to allow it to remove more than one thymine from G·T mismatches. The bound thymine DNA glycosylase prevents human Apurinic endonuclease 1 (HAP1) cutting the Apurinic Site, so unless the glycosylase was displaced, the repair of Apurinic Sites would be very slow. However, HAP1 significantly increases the rate of dissociation of thymine DNA glycosylase from Apurinic Sites, presumably through direct interaction with the bound glycosylase. This effect is concentration-dependent and at the probable normal concentration of HAP1 in cells the dissociation would be fast. This interaction couples the first step in base excision repair, the glycosylase, to the second step, the Apurinic endonuclease. The other proteins involved in base excision repair, polymerase β, XRCC1, and DNA ligase III, do not affect the dissociation of thymine DNA glycosylase from the Apurinic Site.