8 Methylguanine
Mostrando 1-12 de 24 artigos, teses e dissertações.
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1. Correlation of MGMT promoter methylation status with gene and protein expression levels in glioblastoma
OBJECTIVES: 1) To correlate the methylation status of the O6-methylguanine-DNA-methyltransferase (MGMT) promoter to its gene and protein expression levels in glioblastoma and 2) to determine the most reliable method for using MGMT to predict the response to adjuvant therapy in patients with glioblastoma. BACKGROUND: The MGMT gene is epigenetically silenced b
Clinics. Publicado em: 2011
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2. Participação de radicais livres centrados em átomos de carbono na toxicidade de hidrazina / Carbon-centered free radicals participation in hydrazine toxicity
A produção de radicais de carbono "in vivo" durante a biotransformação da hidrazina foi demonstrada por ressonância para magnética eletrônica, utilizando o método do captador de spin. Eritrócitos de rato também oxidaram a hidrazina, formando radicais de carbono e nitrogênio, além de espécies reativas de oxigênio. Todas estas espécies, possivel
Publicado em: 1996
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3. uvrA and recA mutations inhibit a site-specific transition produced by a single O6-methylguanine in gene G of bacteriophage phi X174.
Using site-specific mutagenesis, we have examined the mutagenic activity in vivo of O6-methylguanine or O6-n-butylguanine located at a preselected site in gene G of bacteriophage phi X174. The experiments were designed so that the phage mutant produced by a targeted transition from either of these alkylated derivatives would be recognizable by a simple plaqu
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4. Adaptive increase of O6-methylguanine-acceptor protein in HeLa cells following N-methyl-N'-nitro-N-nitrosoguanidine treatment.
We have assayed in extracts of HeLa cells the amount of acceptor protein that removes O6-methylguanine adducts from alkylated DNA. Cells were treated with single or multiple nontoxic doses of N-methyl-N'-nitrosoguanidine (MNNG) and the extracts were analyzed up to 32 h after the last exposure. The acceptor activity assayed immediately (1 h) after single expo
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5. Bacillus subtilis gene coding for constitutive O6-methylguanine-DNA alkyltransferase.
We have cloned a Bacillus subtilis DNA fragment that could correct the defect in a constitutive O6-methylguanine-DNA alkyltransferase (Dat1). This fragment also corrected the hypersensitivity of the strain TKJ6951(ada-1 dat-1) to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In the fragment, the gene activity resides in a region of about 850 bp which contains
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6. 7-Methylguanine specific tRNA-methyltransferase from Escherichia coli.
A 7-methylguanine (m7G) specific tRNA methyltransferase from E. coli MRE 600 was purified about 1000 fold by affinity chromatography on Sepharose bound with normal E. coli tRNA. The purified enzyme catalyzes exclusively the formation of m7G in submethylated bulk tRNA of E. coli K12 met- rel-. The purified enzyme transfers the methyl group from S-adenosyl-met
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7. Synthesis, structure and thermodynamic properties of 8-methylguanine-containing oligonucleotides: Z-DNA under physiological salt conditions.
Various oligonucleotides containing 8-methylguanine (m8G) have been synthesized and their structures and thermodynamic properties investigated. Introduction Of M8G into DNA sequences markedly stabilizes the Z conformation under low salt conditions. The hexamer d(CGC[M8G]CG)2 exhibits a CD spectrum characteristic of the Z conformation under physiological salt
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8. In situ enzymatic reclosure of opened imidazole rings of purines in DNA damaged by gamma-irradiation.
When aqueous solutions of DNA were treated with 10-500 grays of gamma-rays, the imidazole rings of some adenine and guanine residues underwent scission, resulting in the conversion of these purines to formamidopyrimidines. It was found that formamidopyrimidine-DNA glycosylase, known to remove imidazole-ring-opened 7-methylguanine from DNA, did not excise the
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9. Perturbations of enzymic uracil excision due to purine damage in DNA.
Phage PBS-2 DNA, which contains uracil in place of thymine, was selectively damaged and then used as substrate for purified Bacillus subtilis uracil-DNA glycosylase. This enzyme releases uracil from DNA in a limited processive manner. Irradiation by ultraviolet light (greater than 305 nm) in the presence of isopropanol and a free radical photoinitiator intro
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10. Structural studies of O6-methyldeoxyguanosine and related compounds: a promutagenic DNA lesion by methylating carcinogens.
O6-Methylation of guanine residues in DNA can induce mutations by formation of base mispairing due to the deprotonation of N(1). The electronic, geometric and conformational properties of three N(9)-Substituted O6-methylguanine derivatives, O6-methyldeoxyguanosine (O6mdGuo), O6-methylguanosine (O6mGuo) and O6, 9-dimethylguanine (O6mdGua), were investigated b
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11. Yeast DNA Polymerase ζ Is an Efficient Extender of Primer Ends Opposite from 7,8-Dihydro-8-Oxoguanine and O6-Methylguanine
Genetic studies in Saccharomyces cerevisiae have indicated the requirement of DNA polymerase (Pol) ζ for mutagenesis induced by UV light and by other DNA damaging agents. However, on its own, Polζ is highly inefficient at replicating through DNA lesions; rather, it promotes their mutagenic bypass by extending from the nucleotide inserted opposite the lesio
American Society for Microbiology.
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12. In vivo mutagenesis by O6-methylguanine built into a unique site in a viral genome.
The mutagenicity of O6-methylguanine (O6MeGua), a chemical carcinogen-DNA adduct, has been studied in vivo by using a single-stranded M13mp8 genome in which a single O6MeGua residue was positioned in the unique recognition site for the restriction endonuclease Pst I. Transformation of Escherichia coli MM294A cells with this vector gave progeny phage, of whic