Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Int J Radiat Biol ; 93(3): 295-302, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-27707033

RESUMO

PURPOSE: To clarify whether initial base excision repair processes at clustered DNA damage sites comprising multiple base lesions affect subsequent excision processes via the formation of additional strand breaks by glycosylase and apurinic/apyrimidinic (AP) endonuclease base excision enzymes. MATERIALS AND METHODS: Plasmid DNA (pUC18) as a model DNA molecule was exposed to high-linear-energy-transfer (LET) ionizing radiation (He2+ or C6+ ions) or low-LET ionizing radiation (X-rays) under various conditions to produce varied radical-scavenging effects. pUC18 was then treated sequentially or simultaneously with two bacterial base excision enzymes (glycosylases), namely, endonuclease III and formamidopyrimidine-DNA glycosylase, which convert pyrimidine (or abasic [AP] site) and purine (or AP site) lesions to single-strand breaks (SSB), respectively. Yields of additional SSB or double-strand breaks (DSB) as digestion products were examined after changing the order of enzymatic treatment. RESULTS: There were few differences among the enzymatic treatments, indicating that treatment order did not affect the final yields of additional SSB or DSB formed by glycosylase activity. This suggests that of the total damage, the fraction of clustered damage sites with a persistent base lesion dependent on the order of glycosylase treatment was insignificant if present. CONCLUSION: Base lesion clusters induced by high- or low-LET radiation appear three or more base pairs apart, and are promptly converted to a DSB by glycosylase, regardless of the order of enzymatic treatment.


Assuntos
Dano ao DNA , DNA Glicosilases/química , Reparo do DNA , DNA/química , DNA/efeitos da radiação , Desoxirribonuclease I/química , Pareamento de Bases/efeitos da radiação , DNA Glicosilases/efeitos da radiação , Desoxirribonuclease I/efeitos da radiação , Relação Dose-Resposta à Radiação , Doses de Radiação
2.
Radiat Environ Biophys ; 52(1): 99-112, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23188258

RESUMO

DNA from plasmid pUC18 was irradiated with low-LET (13 keV/µm) or high-LET (60 keV/µm) carbon ions or X-rays (4 keV/µm) in solutions containing several concentrations of Tris (0.66-200 mM) to determine the yield of abasic (AP) sites and the effect of scavenging capacity. The yield of AP sites, detected as single-strand breaks (SSB) after digestion with E. coli endonuclease IV (Nfo), was compared with that of SSB and base lesions. At higher concentrations of Tris, the yields of single or clustered AP sites were significantly lower than those of single or clustered base lesions. The relative yields of single AP sites and AP clusters were less than 10 and 7 %, respectively, of the total damage produced at a scavenger capacity mimicking that in cells. The dependence of the yield of AP sites on scavenging capacity was similar to that of prompt strand breaks. The ratios of the yield of isolated AP sites to that of SSB induced by carbon ion or X-ray irradiation were relatively constant at 0.45 ± 0.15 over the tested range of scavenger capacity, although the ratio of SSB to double-strand breaks (DSB) showed the characteristic dependence on both scavenging capacity and radiation quality. These results indicate that the reaction of water radiolysis products, presumably OH radicals, with the sugar-phosphate moieties in the DNA backbone induces both AP sites and SSB with similar efficiency. Direct ionization of DNA is notably more involved in the production of DSB and base lesion clusters than in the production of AP site clusters.


Assuntos
Carbono/efeitos adversos , Dano ao DNA , Íons Pesados/efeitos adversos , Raios X/efeitos adversos , DNA/metabolismo , DNA/efeitos da radiação , Plasmídeos/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...