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1.
Cancer Radiother ; 14(6-7): 563-70, 2010 Oct.
Artigo em Francês | MEDLINE | ID: mdl-20729117

RESUMO

Image-guided radiotherapy (IGRT) combined or not with intensity-modulated radiation therapy (IMRT) are new and very useful techniques. However, these new techniques are responsible of irradiation at low dose in large volumes. The control of alignment, realignment of the patient and target positioning in external beam radiotherapy are increasingly performed by radiological imaging devices. The management of this medical imaging depends on the practice of each radiotherapy centre. The physical doses due to the IGRT are however quantifiable and traceable. In one hand, these doses appear justified for a better targeting and could be considered negligible in the context of radiotherapy. On the other hand, the potential impact of these low doses should deserve the consideration of professionals. It appears important therefore to report and consider not only doses in target volumes and in "standard" organs at risk, but also the volume of all tissue receiving low doses of radiation. The recent development of IMRT launches the same issue concerning the effects of low doses of radiation. Indeed, IMRT increases the volume of healthy tissue exposed to radiation. At low dose (<100mGy), many parameters have to be considered for health risk estimations: the induction of genes and activation of proteins, bystander effect, radio-adaptation, the specific low-dose radio-hypersensitivity and individual radiation sensitivity. With the exception of the latter, the contribution of these parameters is generally protective in terms of carcinogenesis. An analysis of secondary cancers arising out of field appears to confirm such notion. The risk of secondary tumours is not well known in these conditions of treatment associating IMRT and IGRT. It is therefore recommended that the dose due to imaging during therapeutic irradiation be reported.


Assuntos
Radioterapia Assistida por Computador/métodos , Efeito Espectador , Transformação Celular Neoplásica/efeitos da radiação , Dano ao DNA , Relação Dose-Resposta à Radiação , Desenho de Equipamento , Expressão Gênica/efeitos da radiação , Humanos , Neoplasias Induzidas por Radiação/epidemiologia , Neoplasias Induzidas por Radiação/etiologia , Neoplasias Induzidas por Radiação/prevenção & controle , Segunda Neoplasia Primária/epidemiologia , Segunda Neoplasia Primária/etiologia , Segunda Neoplasia Primária/prevenção & controle , Tamanho do Órgão , Lesões por Radiação/etiologia , Lesões por Radiação/prevenção & controle , Tolerância a Radiação , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador/efeitos adversos , Planejamento da Radioterapia Assistida por Computador/instrumentação , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Assistida por Computador/efeitos adversos , Radioterapia Assistida por Computador/instrumentação , Radioterapia de Intensidade Modulada/efeitos adversos , Radioterapia de Intensidade Modulada/instrumentação , Radioterapia de Intensidade Modulada/métodos , Risco , Carga Tumoral
2.
Eur J Cancer ; 45(3): 354-9, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19081244

RESUMO

This Workshop was organised by the Organisation of European Cancer Institutes (OECI) to provide a forum for discussing the late side-effects resulting from different cancer treatments. One of the main Workshop objectives was to generate recommendations on how to improve knowledge and, consequently, long-term care for cancer survivors.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Neoplasias/terapia , Radioterapia/efeitos adversos , Terapia Combinada , Relação Dose-Resposta a Droga , Relação Dose-Resposta à Radiação , Europa (Continente) , Feminino , Humanos , Masculino , Neoplasias/complicações , Neoplasias Induzidas por Radiação/etiologia , Neoplasias Induzidas por Radiação/terapia , Serviço Hospitalar de Oncologia , Taxa de Sobrevida
3.
Food Chem Toxicol ; 46(2): 446-75, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17996351

RESUMO

Since the middle ages, essential oils have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, medicinal and cosmetic applications, especially nowadays in pharmaceutical, sanitary, cosmetic, agricultural and food industries. Because of the mode of extraction, mostly by distillation from aromatic plants, they contain a variety of volatile molecules such as terpenes and terpenoids, phenol-derived aromatic components and aliphatic components. In vitro physicochemical assays characterise most of them as antioxidants. However, recent work shows that in eukaryotic cells, essential oils can act as prooxidants affecting inner cell membranes and organelles such as mitochondria. Depending on type and concentration, they exhibit cytotoxic effects on living cells but are usually non-genotoxic. In some cases, changes in intracellular redox potential and mitochondrial dysfunction induced by essential oils can be associated with their capacity to exert antigenotoxic effects. These findings suggest that, at least in part, the encountered beneficial effects of essential oils are due to prooxidant effects on the cellular level.


Assuntos
Biologia Molecular/tendências , Óleos Voláteis/efeitos adversos , Animais , Anticarcinógenos/química , Anticarcinógenos/uso terapêutico , Humanos , Testes de Sensibilidade Microbiana , Testes de Mutagenicidade , Óleos Voláteis/química , Óleos Voláteis/farmacologia
5.
Oncogene ; 26(19): 2769-80, 2007 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-17057732

RESUMO

Non-homologous end joining (NHEJ) and homologous recombination (HR) are two pathways that can compete or cooperate for DNA double-strand break (DSB) repair. NHEJ was previously shown to act throughout the cell cycle whereas HR is restricted to late S/G2. Paradoxically, we show here that defect in XRCC4 (NHEJ) leads to over-stimulation of HR when cells were irradiated in G1, not in G2. However, XRCC4 defect did not modify the strict cell cycle regulation for HR (i.e. in S/G2) as attested by (i) the formation of Rad51 foci in late S/G2 whatever the XRCC4 status, and (ii) the fact that neither Rad51 foci nor HR (gene conversion plus single-strand annealing) events induced by ionizing radiation were detected when cells were maintained blocked in G1. Finally, both gamma-H2AX analysis and pulse field gel electrophoresis showed that following irradiation in G1, some DSBs reached S/G2 in NHEJ-defective cells. Taken together, our results show that when cells are defective in G1/S arrest, DSB produced in G1 and left unrepaired by XRCC4 can be processed by HR but in late S/G2.


Assuntos
Quebras de DNA de Cadeia Dupla , Proteínas de Ligação a DNA/fisiologia , Fase G1/genética , Fase G2/genética , Recombinação Genética , Fase S/genética , Animais , Células Cultivadas/efeitos da radiação , Proteínas de Ligação a DNA/genética , Fase G1/efeitos da radiação , Fase G2/efeitos da radiação , Marcação de Genes , Raios Infravermelhos , Camundongos , Camundongos Knockout , Rad51 Recombinase/metabolismo , Fase S/efeitos da radiação
6.
Biochimie ; 88(11): 1549-59, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17070979

RESUMO

Cadmium is an important toxic environmental heavy metal. Occupational and environmental pollution with cadmium results mainly from mining, metallurgy industry and manufactures of nickel-cadmium batteries, pigments and plastic stabilizers. Important sources of human intoxication are cigarette smoke as well as food, water and air contaminations. In humans, cadmium exposures have been associated with cancers of the prostate, lungs and testes. Acute exposures are responsible for damage to these organs. Chronic intoxication is associated with obstructive airway disease, emphysema, irreversible renal failure, bone disorders and immuno-suppression. At the cellular level, cadmium affects proliferation, differentiation and causes apoptosis. It has been classified as a carcinogen by the International Agency for Research on Cancer (IARC). However, it is weakly genotoxic. Indirect effects of cadmium provoke generation of reactive oxygen species (ROS) and DNA damage. Cadmium modulates also gene expression and signal transduction, reduces activities of proteins involved in antioxidant defenses. Several studies have shown that it interferes with DNA repair. The present review focuses on the effects of cadmium in mammalian cells with special emphasis on the induction of damage to DNA, membranes and proteins, the inhibition of different types of DNA repair and the induction of apoptosis. Current data and hypotheses on the mechanisms involved in cadmium genotoxicity and carcinogenesis are outlined.


Assuntos
Cádmio/farmacologia , Cádmio/toxicidade , Reparo do DNA/efeitos dos fármacos , Ciclo Celular/efeitos dos fármacos , Humanos , Mutagênese , Mutagênicos/toxicidade , Estresse Oxidativo/efeitos dos fármacos
7.
J Radiol Prot ; 26(3): 317-24, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-16926474

RESUMO

From December 2004 to July 2005, three reports on the effects of low doses of ionising radiation were released: ICRP (2004), the joint report of the French Academies of Science and Medicine (Tubiana et al 2005), and a report from the American Academy of Sciences (BEIR VII 2005). These reports quote the same recent articles on the biological effects of low doses, yet their conclusions diverge. The French report concludes that recent biological data show that the efficacy of defense mechanisms is modulated by dose and dose rate and that linear no threshold (LNT) is no longer plausible. The ICRP and the BEIR VII reports recognise that there are biologic arguments against LNT but feel that there are not sufficient biological proofs against it to change risk assessment methodology and subsequent regulatory policy based on LNT. They point out the remaining uncertainties and the lack of mechanistic explanations of phenomena such as low dose hyperlethality or the adaptive response. In this context, a critical analysis of the available data is necessary. The epidemiological data and the experimental data challenge the validity of the LNT hypothesis for assessing the carcinogenic effect of low doses, but do not allow its exclusion. Therefore, the main criteria for selecting the most reliable dose-effect relationship from a scientific point of view should be based on biological data. Their analysis should help one to understand the current controversy.


Assuntos
Relação Dose-Resposta à Radiação , Radiação Ionizante , Medição de Risco/métodos , Animais , Humanos , Agências Internacionais , Modelos Lineares , Concentração Máxima Permitida , Neoplasias Induzidas por Radiação/prevenção & controle , Proteção Radiológica/normas
8.
Mutat Res ; 606(1-2): 27-38, 2006 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-16678471

RESUMO

Essential oils (EOs) extracted from medicinal plants such as Origanum compactum, Artemisia herba alba and Cinnamomum camphora are known for their beneficial effects in humans. The present study was undertaken to investigate their possible antigenotoxic effects in an eukaryotic cell system, the yeast Saccharomyces cerevisiae. The EOs alone showed some cytotoxicity and cytoplasmic petite mutations, i.e. mitochondrial damage, but they were unable to induce nuclear genetic events. In combination with exposures to nuclear mutagens such as 254-nm UVC radiation, 8-methoxypsoralen (8-MOP) plus UVA radiation and methylmethane sulfonate (MMS), treatments with these EOs produced a striking increase in the amount of cytoplasmic petite mutations but caused a significant reduction in revertants and mitotic gene convertants induced among survivors of the diploid tester strain D7. In a corresponding rho0 strain, the level of nuclear genetic events induced by the nuclear mutagens UVC and 8-MOP plus UVA resulted in the same reduced level as the combined treatments with the EOs. This clearly suggests a close relationship between the enhancement of cytoplasmic petites (mitochondrial damage) in the presence of the EOs and the reduction of nuclear genetic events induced by UVC or 8-MOP plus UVA. After MMS plus EO treatment, induction of these latter events was comparable at least per surviving fraction in wildtype and rho0 cells, and apparently less dependent on cytoplasmic petite induction. Combined treatments with MMS and EOs clearly triggered switching towards late apoptosis/necrosis indicating an involvement of this phenomenon in EO-induced cell killing and concomitant decreases in nuclear genetic events. After UVC and 8-MOP plus UVA plus EO treatments, little apoptosis and necrosis were observed. The antigenotoxic effects of the EOs appeared to be predominantly linked to the induction of mitochondrial dysfunction.


Assuntos
Diploide , Metoxaleno/farmacologia , Metanossulfonato de Metila/farmacologia , Óleos Voláteis/farmacologia , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos da radiação , Raios Ultravioleta , Apoptose/efeitos dos fármacos , Apoptose/efeitos da radiação , Artemisia/química , Sobrevivência Celular , Cinnamomum camphora/química , Citoplasma/metabolismo , Relação Dose-Resposta a Droga , Relação Dose-Resposta à Radiação , Conversão Gênica/efeitos dos fármacos , Conversão Gênica/efeitos da radiação , Mutagênicos/farmacologia , Necrose , Origanum/química , Mutação Puntual/efeitos dos fármacos , Mutação Puntual/efeitos da radiação , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/genética
9.
Radiat Environ Biophys ; 44(4): 245-51, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16468064

RESUMO

Recently, the risk associated with low doses of ionizing radiation has gained new interest. Here, we analyze and discuss the major differences between two reports recently published on this issue; the report of the French Academy of Sciences and of the French Academy of Medicine published in March 2005, and the BEIR VII-Phase 2 Report of the American National Academy of Sciences published as a preliminary version in July 2005. The conclusion of the French Report is that the linear no-threshold relationship (LNT) may greatly overestimate the carcinogenic effect of low doses (<100 mSv) and even more that of very low doses (<10 mSv), such as those delivered during X-ray examinations. Conversely, the conclusion of the BEIR VII report is that LNT should be used for assessing the detrimental effects of these low and very low doses. The causes of these diverging conclusions should be carefully examined. They seem to be mostly associated with the interpretation of recent biological data. The point of view of the French Report is that these recent data are incompatible with the postulate on which LNT is implicitly based, namely the constancy of the carcinogenic effect per unit dose, irrespective of dose and dose rate.


Assuntos
Ensaios Clínicos como Assunto , Relação Dose-Resposta à Radiação , Modelos Biológicos , Neoplasias Induzidas por Radiação/epidemiologia , Radiação Ionizante , Medição de Risco/métodos , Carga Corporal (Radioterapia) , Simulação por Computador , Humanos , Incidência , Modelos Lineares , Doses de Radiação , Proteção Radiológica/métodos , Eficiência Biológica Relativa , Fatores de Risco
10.
Mutat Res ; 585(1-2): 1-13, 2005 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-15975845

RESUMO

In order to get an insight into the possible genotoxicity of essential oils (EOs) used in traditional pharmacological applications we tested five different oils extracted from the medicinal plants Origanum compactum, Coriandrum sativum, Artemisia herba alba, Cinnamomum camphora (Ravintsara aromatica) and Helichrysum italicum (Calendula officinalis) for genotoxic effects using the yeast Saccharomyces cerevisiae. Clear cytotoxic effects were observed in the diploid yeast strain D7, with the cells being more sensitive to EOs in exponential than in stationary growth phase. The cytotoxicity decreased in the following order: Origanum compactum>Coriandrum sativum>Artemisia herba alba>Cinnamomum camphora>Helichrysum italicum. In the same order, all EOs, except that derived from Helichrysum italicum, clearly induced cytoplasmic petite mutations indicating damage to mitochondrial DNA. However, no nuclear genetic events such as point mutations or mitotic intragenic or intergenic recombination were induced. The capacity of EOs to induce nuclear DNA damage-responsive genes was tested using suitable Lac-Z fusion strains for RNR3 and RAD51, which are genes involved in DNA metabolism and DNA repair, respectively. At equitoxic doses, all EOs demonstrated significant gene induction, approximately the same as that caused by hydrogen peroxide, but much lower than that caused by methyl methanesulfonate (MMS). EOs affect mitochondrial structure and function and can stimulate the transcriptional expression of DNA damage-responsive genes. The induction of mitochondrial damage by EOs appears to be closely linked to overall cellular cytotoxicity and appears to mask the occurrence of nuclear genetic events. EO-induced cytotoxicity involves oxidative stress, as is evident from the protection observed in the presence of ROS inhibitors such as glutathione, catalase or the iron-chelating agent deferoxamine.


Assuntos
Óleos Voláteis/toxicidade , Saccharomyces cerevisiae/genética , Catalase/metabolismo , Catalase/farmacologia , Citoplasma/genética , Dano ao DNA/genética , Reparo do DNA , DNA Mitocondrial/efeitos dos fármacos , Proteínas de Ligação a DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/genética , Desferroxamina/metabolismo , Desferroxamina/farmacologia , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Glutationa/metabolismo , Glutationa/farmacologia , Peróxido de Hidrogênio/metabolismo , Peróxido de Hidrogênio/farmacologia , Mutação , Óleos Voláteis/farmacologia , Plantas Medicinais/química , Rad51 Recombinase , Espécies Reativas de Oxigênio/metabolismo , Proteínas Recombinantes de Fusão/efeitos dos fármacos , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Recombinação Genética , Ribonucleotídeo Redutases/efeitos dos fármacos , Ribonucleotídeo Redutases/genética , Saccharomyces cerevisiae/efeitos dos fármacos , Proteínas de Saccharomyces cerevisiae , Testes de Toxicidade , Ativação Transcricional , beta-Galactosidase/efeitos dos fármacos , beta-Galactosidase/genética , beta-Galactosidase/metabolismo
11.
EMBO J ; 20(14): 3861-70, 2001 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-11447127

RESUMO

To analyze relationships between replication and homologous recombination in mammalian cells, we used replication inhibitors to treat mouse and hamster cell lines containing tandem repeat recombination substrates. In the first step, few double-strand breaks (DSBs) are produced, recombination is slightly increased, but cell lines defective in non-homologous end-joining (NHEJ) affected in ku86 (xrs6) or xrcc4 (XR-1) genes show enhanced sensitivity to replication inhibitors. In the second step, replication inhibition leads to coordinated kinetics of DSB accumulation, Rad51 foci formation and RAD51-dependent gene conversion stimulation. In xrs6 as well as XR-1 cell lines, Rad51 foci accumulate more rapidly compared with their respective controls. We propose that replication inhibition produces DSBs, which are first processed by the NHEJ; then, following DSB accumulation, RAD51 recombination can act.


Assuntos
Replicação do DNA , Recombinação Genética , Animais , Afidicolina/farmacologia , Linhagem Celular , Ensaio Cometa , Cricetinae , Dano ao DNA , Reparo do DNA/fisiologia , Replicação do DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/fisiologia , Fase G1/efeitos dos fármacos , Hidroxiureia/farmacologia , Camundongos , Mimosina/farmacologia , Rad51 Recombinase , Fase S/efeitos dos fármacos
12.
Cancer Radiother ; 4(5): 335-54, 2000.
Artigo em Francês | MEDLINE | ID: mdl-11098222

RESUMO

Cells of higher eukaryotes possess several very efficient systems for the repair of radiation-induced lesions in DNA. Different strategies have been adopted at the cellular level to remove or even tolerate various types of lesions in order to assure survival and limit the mutagenic consequences. In mammalian cells, the main DNA repair systems comprise direct reversion of damage, excision of damage and exchange mechanisms with intact DNA. Among these, the direct ligation of single strand breaks (SSB) by a DNA ligase and the multi-enzymatic repair systems of mismatch repair, base and nucleotide excision repair as well as the repair of double strand breaks (DSB) by homologous recombination or non homologous end-joining are the most important systems. Most of these processes are error-free except the non homologous end-joining pathway used mainly for the repair of DSB. Moreover, certain lesions can be tolerated by more or less accurately acting polymerases capable of performing translesional DNA syntheses. The DNA repair systems are intimately integrated in the network of cellular regulation. Some of their components are DNA damage inducible. Radiation-induced mutagenesis is largely due to unrepaired DNA damage but also involves error-prone repair processes like the repair of DSB by non-homologous end-joining. Generally, mammalian cells are well prepared to repair radiation-induced lesions. However, some questions remain to be asked about mechanistic details and efficiencies of the systems for removing certain types of radiation-damage and about their order and timing of action. The answers to these questions would be important for radioprotection as well as radiotherapy.


Assuntos
Reparo do DNA/fisiologia , DNA/efeitos da radiação , Células Eucarióticas/efeitos da radiação , Mutagênese/efeitos da radiação , Animais , Dano ao DNA/fisiologia , Humanos
14.
Int J Radiat Biol ; 76(7): 901-12, 2000 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10923614

RESUMO

PURPOSE: To determine how radiation-induced arrest in G2 affects the response of mammalian cells to a challenging dose of radiation or to antitumour drugs producing DNA double-strand breaks. MATERIALS AND METHODS: V79 fibroblast survival to 5 Gy gamma-rays followed at intervals by 3 Gy irradiation or by contact with an equitoxic dose of neocarzinostatin or etoposide, was measured by clonogenic assays. The pattern of radiation-induced DNA double-strand breaks was determined by filter elution and CFGE (continuous field gel electrophoresis) or PFGE (pulsed-field gel electrophoresis) in G2-arrested cells as well as in nonpre-irradiated asynchronous or synchronized cells. The cell-cycle phase specificity of drug susceptibility was determined in synchronized HeLa cells. RESULTS: Cell kill by radiation-drug combined treatment varied markedly with the time elapsed after priming irradiation. Pre-irradiated, G2-arrested V79 fibroblasts demonstrated excess double-stranded DNA cleavage upon re-irradiation and hypersensitivity to drugs and radiation, although maximum resistance to both neocarzinostatin and etoposide in synchronized HeLa cells was in G2. This effect occurred in the megabase range only, with a peak around 4 Mbp; no change in the electrophoretic migration profile of DNA was observed below 1 Mbp. Moreover, the DNA migration profile and the yield of DNA cleavage in G2-arrested cells were close to those expected from S-phase cells. CONCLUSION: The available data suggest that mechanisms operating within the radiation-induced G2 block promote susceptibility to DNA double-strand break inducers at this stage. It is also proposed that the conformation of DNA in cells accumulated in G2 following irradiation bears resemblance to that for cells in S phase, due either to active repair mechanisms or to inhibition of chromosome disentanglement at the S-G2 transition.


Assuntos
Dano ao DNA , DNA/efeitos da radiação , Fase G2/efeitos da radiação , Animais , Cricetinae , DNA/efeitos dos fármacos , Células HeLa , Humanos
15.
Genetics ; 154(3): 1085-99, 2000 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10757755

RESUMO

Chromosomal repair was studied in stationary-phase Saccharomyces cerevisiae, including rad52/rad52 mutant strains deficient in repairing double-strand breaks (DSBs) by homologous recombination. Mutant strains suffered more chromosomal fragmentation than RAD52/RAD52 strains after treatments with cobalt-60 gamma irradiation or radiomimetic bleomycin, except after high bleomycin doses when chromosomes from rad52/rad52 strains contained fewer DSBs than chromosomes from RAD52/RAD52 strains. DNAs from both genotypes exhibited quick rejoining following gamma irradiation and sedimentation in isokinetic alkaline sucrose gradients, but only chromosomes from RAD52/RAD52 strains exhibited slower rejoining (10 min to 4 hr in growth medium). Chromosomal DSBs introduced by gamma irradiation and bleomycin were analyzed after pulsed-field gel electrophoresis. After equitoxic damage by both DNA-damaging agents, chromosomes in rad52/rad52 cells were reconstructed under nongrowth conditions [liquid holding (LH)]. Up to 100% of DSBs were eliminated and survival increased in RAD52/RAD52 and rad52/rad52 strains. After low doses, chromosomes were sometimes degraded and reconstructed during LH. Chromosomal reconstruction in rad52/rad52 strains was dose dependent after gamma irradiation, but greater after high, rather than low, bleomycin doses with or without LH. These results suggest that a threshold of DSBs is the requisite signal for DNA-damage-inducible repair, and that nonhomologous end-joining repair or another repair function is a dominant mechanism in S. cerevisiae when homologous recombination is impaired.


Assuntos
Dano ao DNA , Reparo do DNA , DNA Fúngico , Proteínas de Ligação a DNA/fisiologia , Proteínas Fúngicas/fisiologia , Saccharomyces cerevisiae/genética , Bleomicina/farmacologia , Cromossomos Fúngicos , Dano ao DNA/efeitos dos fármacos , Dano ao DNA/efeitos da radiação , Fragmentação do DNA , DNA Fúngico/efeitos dos fármacos , DNA Fúngico/efeitos da radiação , DNA de Cadeia Simples , Proteínas de Ligação a DNA/genética , Eletroforese em Gel de Campo Pulsado , Proteínas Fúngicas/genética , Proteína Rad52 de Recombinação e Reparo de DNA , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/efeitos da radiação , Proteínas de Saccharomyces cerevisiae , Fatores de Tempo
16.
Yeast ; 16(3): 267-76, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10649455

RESUMO

The disruption of six novel yeast genes has been realized in two genetic backgrounds. Six open reading frames (ORFs) from chromosome IV, YDR013w, YDR014w, YDR015c, YDR018c, YDR020c and YDR021w, were disrupted using the KanMX4 marker and PCR-targeting with long flanking regions homologous (LFH) to the target locus. The deletants were verified at the molecular level, using PCR and Southern analysis. Sporulation and tetrad analysis revealed that ORFs YDR013w and YDR021w (also known as FAL1) are essential genes. Microscopical observations showed that ydr013wDelta haploid cells were blocked after one or two cell cycles and presented heterogeneous bud sizes. The ydr021wDelta haploid cells gave rise to microcolonies of about 20 cells. The other four ORFs are non-essential. Basic phenotypic analysis of the non-lethal deletant strains did not reveal any significant differences in cell morphology, growth on different media and temperatures, sporulation and mating efficiency between parental and mutant strains in the FY1679 background.


Assuntos
Deleção de Genes , Genes Fúngicos , Fases de Leitura Aberta/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Southern Blotting , Cromossomos Fúngicos/genética , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/fisiologia , Fenótipo , Reação em Cadeia da Polimerase , Saccharomyces cerevisiae/crescimento & desenvolvimento
17.
Cancer Radiother ; 3(4): 289-95, 1999.
Artigo em Francês | MEDLINE | ID: mdl-10486539

RESUMO

Repair pathways of DNA are now better defined, and some important findings have been discovered in the last few years. DNA non-homologous end-joining (NEHJ) is a crucial process in the repair of radiation-induced double-strand breaks (DSBs). NHEJ implies at least three steps: the DNA free-ends must get closer, preparation of the free-ends by exonucleases and then a transient hybridisation in a region of DNA with weak homology. DNA-dependent protein kinase (DNA-PK) is the key enzyme in this process. DNA-PK is a nuclear serine/threonine kinase that comprises three components: a catlytic subunit (DNA-PKCS) and two regulatory subunits, DNA-binding proteins, Ku80 and Ku70. The severe combined immunodeficient (scid) mice are deficient in DNA-PKCS: this protein is involved both in DNA repair and in the V(D)J recombination of immunoglobulin and T-cell receptor genes. It is a protein-kinase of the P13-kinase family and which can phosphorylates Ku proteins, p53 and probably some other proteins still unknown. DNA-PK is an important actor of DSBs repair (induced by ionising radiations or by drugs like etoposide), but obviously it is not the only mechanism existing in the cell for this function. Some others, like homologous recombination, seem also to have a great importance for cell survival.


Assuntos
Reparo do DNA , Proteínas de Ligação a DNA , DNA/metabolismo , Proteínas Serina-Treonina Quinases/fisiologia , Androstadienos/farmacologia , Animais , Linhagem Celular , Dano ao DNA , Proteína Quinase Ativada por DNA , Dimerização , Humanos , Camundongos , Camundongos SCID , Proteínas Nucleares , Fosforilação , Processamento de Proteína Pós-Traducional , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/química , Wortmanina , Xeroderma Pigmentoso/patologia
18.
C R Acad Sci III ; 321(4): 313-8, 1998 Apr.
Artigo em Francês | MEDLINE | ID: mdl-9766197

RESUMO

The poly (ADP-ribose) polymerase is an ubiquitous nuclear protein capable of binding specifically to DNA strand breaks. It synthesizes ADP-ribose polymers proportionally to DNA breaks. The actual method of reference to determine DNA double strand breaks is pulsed-field gel electrophoresis, but this requires many cells. It thus appeared of interest to use poly (ADP-ribos)ylation to follow and estimate gamma-ray-induced DNA fragmentation at the level of isolated cells after gamma-irradiation in chinese hamster ovary cells (CHO-K1). The results obtained by the immunolabelling technique of ADP-ribose polymers were compared to those obtained by pulsed-field gel electrophoresis. They show that poly (ADP-ribos)ylation reflects the occurrence of radiation-induced DNA strand breaks. A clear relationship exists between the amount of ADP-ribose polymers detected and DNA double strand breaks after gamma-irradiation.


Assuntos
Fragmentação do DNA , DNA/efeitos da radiação , Eletroforese em Gel de Campo Pulsado , Imunoensaio , Poli Adenosina Difosfato Ribose/análise , Animais , Anticorpos Monoclonais , Células CHO , Cricetinae , Imunofluorescência , Raios gama , Microscopia Confocal
19.
Photochem Photobiol ; 68(3): 289-95, 1998 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-9747584

RESUMO

The induction and repair of different types of photodamage and photogenotoxicity in eukaryotic cells have been the subject of many studies. Little is known about possible links between these phenomena and the induction of DNA damage-inducible genes. We explored this relationship using the yeast Saccharomyces cerevisiae, a pertinent eukaryotic model. Previous results showed that the photogenotoxic potential of 8-methoxypsoralen (8-MOP) plus UVA is higher than that of UV (254 nm). Moreover, the induction of the ribonucleotide reductase gene RNR2 by UV and 8-MOP plus UVA in an RNR2-LACZ fusion strain and the formation of DNA double-strand breaks (dsb) as repair intermediates after such treatments suggest that the latter process could involve a signal for gene induction. To further substantiate this, we measured the induction of the DNA repair gene RAD51 in RAD51-LACZ fusion strains using the dsb repair and recombination deficient mutant rad52 and the corresponding wild type, and we determined the formation of dsb by pulsed-field gel electrophoresis. After treatments, the resealing of dsb formed as repair intermediates was impaired in the rad52 mutant. At equal doses, i.e. the same number of lesions, the induction of the RAD51 gene by UV or 8-MOP plus UVA was significantly reduced in the rad52 mutant as compared with the wild type. The same was true when equitoxic doses were used. Thus, the RAD52 repair pathway appears to play an important role not only in dsb repair but also in gene induction. Furthermore, the signaling pathways initiated by DNA damage and its processing are somewhat linked to the photogenotoxic response.


Assuntos
Dano ao DNA , Reparo do DNA , Regulação Fúngica da Expressão Gênica/efeitos da radiação , Metoxaleno/farmacologia , Saccharomyces cerevisiae/genética , Raios Ultravioleta , Divisão Celular/efeitos dos fármacos , Proteínas de Ligação a DNA/genética , Regulação Fúngica da Expressão Gênica/efeitos dos fármacos , Fármacos Fotossensibilizantes/farmacologia , Rad51 Recombinase , Proteínas Recombinantes de Fusão/biossíntese , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/efeitos da radiação , Proteínas de Saccharomyces cerevisiae , Ativação Transcricional
20.
Curr Genet ; 34(1): 30-42, 1998 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9683673

RESUMO

Mitotic recombination within the ARG4 gene of Saccharomyces cerevisiae was analysed after treatment of cells with the recombinogenic agent 8-methoxypsoralen (8-MOP) plus UVA. The appearance of DNA double-strand breaks (DSBs) in the ARG4 region during post-treatment incubation was also tested. The results obtained after 8-MOP plus UVA treatment indicate that in mitotic cells: (1) recombination at the ARG4 locus is increased 30 - 500 fold per survivor depending on the strains and the doses employed, (2) the increase of recombination results essentially from gene conversion events which involve the RV site located in the 5' region of the ARG4 gene twice as often as the Bgl site at the 3' end, (3) depending on 8-MOP/UVA dose, ectopic gene conversion is associated with reciprocal translocation, (4) DSBs occur preferentially in the ARG 5' region during post-treatment incubation, as well as in other intergenic regions containing both promoters or/and terminators of transcription, and (5) changes in sequence content in the 5' region of ARG4, which influences positions and frequencies of DSBs formed during repair, are correlated with a modification of the local chromatin structure.


Assuntos
Dano ao DNA , Proteínas Fúngicas/genética , Metoxaleno/farmacologia , Mitose/genética , Recombinação Genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Raios Ultravioleta , Argininossuccinato Liase , Southern Blotting , Troca Genética , Enzimas de Restrição do DNA/metabolismo , DNA Fúngico/efeitos dos fármacos , DNA Fúngico/efeitos da radiação , Conversão Gênica , Fármacos Fotossensibilizantes/farmacologia , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/efeitos da radiação
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