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1.
Bracesco N Candreva EC Keszenman D Sánchez AG Soria S Dell M Siede W Nunes E 《Radiation and environmental biophysics》2007,46(4):401-407
Checkpoints are components of signalling pathways involved in genome stability. We analysed the putative dual functions of
Rad17 and Chk1 as checkpoints and in DNA repair using mutant strains of Saccharomyces cerevisiae. Logarithmic populations of the diploid checkpoint-deficient mutants, chk1Δ/chk1Δ and rad17Δ/rad17Δ, and an isogenic wild-type strain were exposed to the radiomimetic agent bleomycin (BLM). DNA double-strand breaks (DSBs)
determined by pulsed-field electrophoresis, surviving fractions, and proliferation kinetics were measured immediately after
treatments or after incubation in nutrient medium in the presence or absence of cycloheximide (CHX). The DSBs induced by BLM
were reduced in the wild-type strain as a function of incubation time after treatment, with chromosomal repair inhibited by
CHX. rad17Δ/rad17Δ cells exposed to low BLM concentrations showed no DSB repair, low survival, and CHX had no effect. Conversely, rad17Δ/rad17Δ cells exposed to high BLM concentrations showed DSB repair inhibited by CHX. chk1Δ/chk1Δ cells showed DSB repair, and CHX had no effect; these cells displayed the lowest survival following high BLM concentrations.
Present results indicate that Rad17 is essential for inducible DSB repair after low BLM-concentrations (low levels of oxidative
damage). The observations in the chk1Δ/chk1Δ mutant strain suggest that constitutive nonhomologous end-joining is involved in the repair of BLM-induced DSBs. The differential
expression of DNA repair and survival in checkpoint mutants as compared to wild-type cells suggests the presence of a regulatory
switch-network that controls and channels DSB repair to alternative pathways, depending on the magnitude of the DNA damage
and genetic background.
Nelson Bracesco and Ema C. Candreva have contributed equally to this article. 相似文献
2.
The<Emphasis Type="Italic">atspo11-1</Emphasis> mutation rescues <Emphasis Type="Italic">atxrcc3</Emphasis> meiotic chromosome fragmentation 总被引:2,自引:0,他引:2
Homologous recombination events occurring during meiotic prophase I ensure the proper segregation of homologous chromosomes at the first meiotic division. These events are initiated by programmed double-strand breaks produced by the Spo11 protein and repair of such breaks by homologous recombination requires a strand exchange activity provided by the Rad51 protein. We have recently reported that the absence of AtXrcc3, an ArabidopsisRad51 paralogue, leads to extensive chromosome fragmentation during meiosis, first visible in diplotene of meiotic prophase I. The present study clearly shows that this fragmentation results from un- or mis-repaired AtSpo11-1 induced double-strand breaks and is thus due to a specific defect in the meiotic recombination process. 相似文献
3.
Antimicrobial efficacy of ultra-high-pressure (UHP) can be enhanced by application of additional hurdles. The objective of this study was to systematically assess the enhancement in pressure lethality by TBHQ treatment, against barotolerant strains of Escherichia coli O157:H7 and Listeria monocytogenes. Two L. monocytogenes Scott A and the barotolerant OSY-328 strain, and two E. coli O157:H7 strains, EDL-933 and its barotolerant mutant, OSY-ASM, were tested. Cell suspensions containing TBHQ (50 ppm, dissolved in dimethyl sulfoxide) were pressurized at 200 to 500 MPa (23+/-2 degrees C) for 1 min, plated on tryptose agar and enumerated the survivors. The TBHQ-UHP combination resulted in synergistic inactivation of both pathogens, with different degrees of lethality among strains. The pressure lethality threshold, for the combination treatment, was lower for E. coli O157:H7 (> or = 200 MPa) than for L. monocytogenes (> 300 MPa). E. coli O157:H7 strains were extremely sensitive to the TBHQ-UHP treatment, compared to Listeria strains. Interestingly, a control treatment involving DMSO-UHP combination consistently resulted in higher inactivation than that achieved by UHP alone, against all strains tested. However, sensitization of the pathogens to UHP by the additives (TBHQ in DMSO) was prominently greater for UHP than DMSO. Differences in sensitivities to the treatment between these two pathogens may be attributed to discrepancies in cellular structure or physiological functions. 相似文献
4.
Nowacka-Zawisza M Bryś M Romanowicz-Makowska H Kulig A Krajewska WM 《Cellular & molecular biology letters》2007,12(2):192-205
Breast cancer is the most prevalent cancer type in women. Accumulating evidence indicates that the fidelity of double-strand
break repair in response to DNA damage is an important step in mammary neoplasias. The RAD51 and BRCA1 proteins are involved
in the repair of double-strand DNA breaks by homologous recombination. In this study, we evaluated loss of heterozygosity
(LOH) in the RAD51 and BRCA1 regions, and their association with breast cancer. The polymorphic markers D15S118, D15S214 and D15S1006 were the focus for
RAD51, and D17S855 and D17S1323 for BRCA1. Genomic deletion detected by allelic loss varied according to the regions tested, and ranged from 29 to 46% of informative
cases for the RAD51 region and from 38 to 42% of informative cases for the BRCA1 region. 25% of breast cancer cases displayed LOH for at least one studied marker in the RAD51 region exclusively. On the other hand, 31% of breast cancer cases manifested LOH for at least one microsatellite marker concomitantly
in the RAD51 and BRCA1 regions. LOH in the RAD51 region, similarly as in the BRCA1 region, appeared to correlate with steroid receptor status. The obtained results indicate that alteration in the RAD51 region may contribute to the disturbances of DNA repair involving RAD51 and BRCA1 and thus enhance the risk of breast cancer development. 相似文献
5.
Nehme N Mathieu F Taillandier P 《Journal of industrial microbiology & biotechnology》2008,35(7):685-693
This study examines the interactions that occur between Saccharomyces cerevisiae and Oenococcus oeni strains during the process of winemaking. Various yeast/bacteria pairs were studied by applying a sequential fermentation strategy which simulated the natural winemaking process. First, four yeast strains were tested in the presence of one bacterial strain leading to the inhibition of the bacterial component. The extent of inhibition varied widely from one pair to another and closely depended on the specific yeast strain chosen. Inhibition was correlated to weak bacterial growth rather than a reduction in the bacterial malolactic activity. Three of the four yeast strains were then grown with another bacteria strain. Contrary to the first results, this led to the bacterial stimulation, thus highlighting the importance of the bacteria strain. The biochemical profile of the four yeast fermented media exhibited slight variations in ethanol, SO(2) and fatty acids produced as well as assimilable consumed nitrogen. These parameters were not the only factors responsible for the malolactic fermentation inhibition observed with the first bacteria strain. The stimulation of the second has not been reported before in such conditions and remains unexplained. 相似文献
6.
Genes in the RAD52 epistasis group are involved in repairing DNA double-stranded breaks via homologous recombination. We have previously shown
that RAD50 is involved in mitotic nonhomologous integration but not in homologous integration. However, the role of Rad50 in nonhomologous
integration has not previously been examined. In the current work, we report that the rad50∆ mutation caused a tenfold decrease in the frequency of nonhomologous integration with the majority of nonhomologous integrants
showing an unstable Ura+ phenotype. Sequencing analysis of the integration target sites showed that integration events of both ends of the integrating
vector in the rad50∆ mutant occurred at different chromosomal locations, resulting in large deletions or translocations on the genomic insertion
sites. Interestingly, 47% of events in the rad50∆ mutant were integrated into repetitive sequences including rDNA locus, telomeres and Ty elements and 27% of events were integrated
into non-repetitive sequences as compared to 11% of events integrated into rDNA and 70% into non-repetitive sequences in the
wild-type cells. These results showed that deletion of RAD50 significantly changes the distribution of different classes of integration events, suggesting that Rad50 is required for
nonhomologous integration at non-repetitive sequences more so than at repetitive ones. Furthermore, Southern analysis indicated
that half of the events contained deletions at one or at both ends of the integrating DNA fragment, suggesting that Rad50
might have a role in protecting free ends of double-strand breaks. In contrast to the rad50∆ mutant, the rad50S mutant (separation of function allele) slightly increases the frequency of nonhomologous integration but the distribution
of integration events is similar to that of wild-type cells with the majority of events integrated into a chromosomal locus.
Our results suggest that deletion of RAD50 may block the major pathway of nonhomologous integration into a non-repetitive chromosomal locus and Rad50 may be involved
in tethering two ends of the integrating DNA into close proximity that facilitates nonhomologous integration of both ends
into a single chromosomal locus. 相似文献
7.
Godai Shumoto Keiichi Ueda Sayaka Yamaguchi Takashi Kaneshima Toshihiro Konno Yoshie Terashima Atsushi Yamamoto Luciene A. Nagashima Eiko N. Itano Ayako Sano 《Mycopathologia》2018,183(5):793-803
Paracoccidioidomycosis ceti is a cutaneous disease of cetaceans caused by uncultivated Paracoccidioides brasiliensis or Paracoccidioides spp. Serological cross-reactions between paracoccidioidomycosis ceti and paracoccidioidomycosis, paracoccidioidomycosis and histoplasmosis, and paracoccidioidomycosis and coccidioidomycosis have been reported before. The present study aimed to detect immunohistochemical cross-reaction between antibodies to Paracoccidioides sp. and Histoplasma capsulatum, and vice versa. Thirty murine sera, obtained from experimental infections of 6 isolates of H. capsulatum, were reacted with paraffin-embedded yeast-form cells of Paracoccidioides sp. derived from a case of paracoccidioidomycosis ceti in Japan. The murine sera were also reacted with human isolates of H. capsulatum yeast cells, with P. brasiliensis yeast cells, and with fungal cells of Coccidioides posadasii. Three dolphins’ sera from cases of paracoccidioidomycosis ceti, two human sera from patients with paracoccidioidomycosis, and a serum from a healthy person with a history of coccidioidomycosis were used in order to determine that the tested fungal cells reacted properly. Sera derived from mice infected with an isolate of H. capsulatum reacted positively against yeast cells of Paracoccidioides sp., yeast cells of P. brasiliensis, and fungal cells of C. posadasii, while those derived from other strains were negative. The present study recorded for the first time the cross-reaction between the yeast cells of H. capsulatum and antibodies against Paracoccidioides spp., the yeast cells of Paracoccidioides sp. and antibodies against H. capsulatum, the yeast cells of Paracoccidioides sp. and antibodies against Coccidioides sp., and fungal cells of C. posadasii and antibodies against Paracoccidioides spp. 相似文献
8.
The expansion of trinucleotide repeat sequences associated with hereditary neurological diseases is believed from earlier studies to be due to errors in DNA replication. However, more recent studies have indicated that recombination may play a significant role in triplet repeat expansion. CAG repeat tracts have been shown to induce double-strand breaks (DSBs) during meiosis in yeast, and DSB formation is dependent on the meiotic recombination machinery. The rate of meiotic instability is several fold higher than mitotic instability. To determine whether DSB repair is responsible for the high rate of repeat tract-length alterations, the frequencies of meiotic repeat-tract instability were compared in wild-type and spo11 mutant strains. In the spo11 background, the rate of meiotic repeat-tract instability remained at the mitotic level, suggesting that meiotic alterations of CAG repeat tracts in yeast occur by the recombination mechanism. Several of these meiotic tract-length alterations are due to DSB repair involving use of the sister chromatid as a template. 相似文献
9.
The effect of hydrogen peroxide on the activity of soxRS and oxyR regulon enzymes in different strains of Escherichia coli has been studied. Treatment of bacteria with 20 μM H2O2 caused an increase in catalase and peroxidase activities (oxyR regulon) in all strains investigated. It is shown for the first time that oxidative stress induced by hydrogen peroxide causes
in some E. coli strains a small increase in activity of superoxide dismutase and glucose-6-phosphate dehydrogenase (soxRS regulon). This effect is cancelled by chloramphenicol, an inhibitor of protein synthesis in prokaryotes. The increase in
soxRS regulon enzyme activities was not found in the strain lacking the soxR gene. These results provide evidence for the involvement of the soxRS regulon in the adaptive response of E. coli to oxidative stress induced by hydrogen peroxide.
__________
Translated from Biokhimiya, Vol. 70, No. 11, 2005, pp. 1506–1513.
Original Russian Text Copyright ? 2005 by Semchyshyn, Bagnyukova, Lushchak. 相似文献
10.
Assembly of DNA into chromatin allows for the formation of a barrier that protects naked DNA from protein and chemical agents
geared to degrade or metabolize DNA. Chromatin assembly occurs whenever a length of DNA becomes exposed to the cellular elements,
whether during DNA synthesis or repair. This report describes tools to study chromatin assembly in the model systemSaccharomyces cerevisiae. Modifications to anin vitro chromatin assembly assay are described that allowed a brute force screen of temperature sensitive (ts) yeast strains in order to identify chromatin assembly defective extracts. This screen yielded mutations in genes encoding
two ubiquitin protein ligases (E3s):RSP5, and a subunit of the Anaphase Promoting Complex (APC),APC5. Additional modifications are described that allow for a rapid analysis and anin vivo characterization of yeast chromatin assembly mutants, as well as any other mutant of interest. Our analysis suggests that
thein vitro andin vivo chromatin assembly assays are responsive to different cellular signals, including cell cycle cues that involve different
molecular networks.
Published: July 3, 2003 相似文献
11.
The earlier identified gene RAD31 was mapped on the right arm of chromosome II in the region of gene MEC1 localization. Epistatic analysis demonstrated that the rad31 mutation is an allele of the MEC1 gene, which allows further designation of the rad31 mutation as mec1-212. Mutation mec1-212, similar to deletion alleles of this gene, causes sensitivity to hydroxyurea, disturbs the check-point function, and suppresses
UV-induced mutagenesis. However, this mutation significantly increases the frequency of spontaneous canavanine-resistance
mutations induced by disturbances in correcting errors of DNA replication and repair, which distinguishes it from all identified
alleles of gene MEC1. 相似文献
12.
Laurent X Nouvel Tiago Dos Vultos Eric Kassa-Kelembho Jean Rauzier Brigitte Gicquel 《BMC microbiology》2007,7(1):39
Background
Previous studies have suggested that variations in DNA repair genes of W-Beijing strains may have led to transient mutator phenotypes which in turn may have contributed to host adaptation of this strain family. Single nucleotide polymorphism (SNP) in the DNA repair gene mutT1 was identified in MDR-prone strains from the Central African Republic. A Mycobacteriumtuberculosis H37Rv mutant inactivated in two DNA repair genes, namely ada/alkA and ogt, was shown to display a hypermutator phenotype. We then looked for polymorphisms in these genes in Central African Republic strains (CAR). 相似文献13.
14.
15.
The relationship between Sporidiobolus johnsonii and S. salmonicolor was investigated using rDNA sequence data. Two statistically well-supported clades were obtained. One clade included the
type strain of S. johnsonii and the other included the type strain of S. salmonicolor. However, some mating strains of S. salmonicolor were found in the S. johnsonii group. These strains belonged to mating type A2 and were sexually compatible with mating type A1 strains from the S. salmonicolor group. DNA–DNA reassociation values were high within each clade and moderate between the two clades. In the re-investigation
of teliospore germination, we observed that the basidia of S. salmonicolor were two-celled. In S. johnsonii, basidia were not formed and teliospore germination resulted in direct formation of yeast cells. We hypothesize that the
S. johnsonii clade is becoming genetically isolated from the S. salmonicolor group and that a speciation process is presently going on. We suspect that the observed sexual compatibility between strains
of the S. johnsonii and S. salmonicolor groups and the possible genetic flow between the two species has little biological relevance because distinct phenotypes
have been fixed in the two taxa and intermediate (hybrid) sequences for LSU and ITS rDNAs have not been detected.
An erratum to this article can be found at 相似文献
16.
A. Yu. Chernenkov L. M. Gracheva T. A. Evstyukhina S. V. Koval’tsova V. T. Peshekhonov I. V. Fedorova V. G. Korolev 《Russian Journal of Genetics》2012,48(2):139-145
In eukaryotes, damage tolerance of matrix DNA is mainly determined by the repair pathway under the control of the RAD6 epistatic group of genes. This pathway is also a main source of mutations generated by mutagenic factors. The results of
our recent studies show that gene HSM3 participating in the control of adaptive mutagenesis increases the frequency of mutations induced by different mutagens.
Mutations rad18, rev3, and mms2 controlling various stages of the RAD6 pathway are epistatic with mutation hsm3 that decreases UV-induced mutagenesis to the level typical for single radiation-sensitive mutants. The level of mutagenesis
in the double mutant srs2 hsm3 was lower than in both single mutants. Note that a decrease in the level of mutagenesis relative to the single mutant srs2 depends on the mismatch repair, since this level in the triple mutant srs2 hsm3 pms1 corresponds to that in the single mutant srs2. These data show that the mutator phenotype hsm3 is probably determined by processes occurring in a D loop. In a number of current works, the protein Hsm3 was shown to participate
in the assembly of the proteasome complex S26. The assembly of proteasomes is governed by the N-terminal domain. Our results
demonstrated that the Hsm3 protein contains at least two domains; the N-terminal part of the domain is responsible for the
proteasome assembly, whereas the C-terminal portion of the protein is responsible for mutagenesis. 相似文献
17.
The human cancer susceptibility gene, BRCA2, functions in double-strand break repair by homologous recombination, and it appears to function via interaction of a repetitive
region (“BRC repeats”) with RAD-51. A putatively simpler homolog, dmbrca2, was identified in Drosophila melanogaster recently and also affects mitotic and meiotic double-strand break repair. In this study, we examined patterns of repeat variation
both within Drosophila pseudoobscura and among available Drosophila genome sequences. We identified extensive variation within and among closely related Drosophila
species in BRC repeat number, to the extent that variation within this genus recapitulates the extent of variation found across
the entire animal kingdom. We describe patterns of evolution across species by documenting recent repeat expansions (sometimes
in tandem arrays) and homogenizations within available genome sequences. Overall, we have documented patterns and modes of
evolution in a new model system of a gene which is important to human health. 相似文献
18.
Shockey J Chapital D Gidda S Mason C Davis G Klasson KT Cao H Mullen R Dyer J 《Applied microbiology and biotechnology》2011,92(6):1207-1217
Saccharomyces cerevisiae is frequently used as a bioreactor for conversion of exogenously acquired metabolites into value-added products, but has
not been utilized for bioconversion of low-cost lipids such as triacylglycerols (TAGs) because the cells are typically unable
to acquire these lipid substrates from the growth media. To help circumvent this limitation, the Yarrowia lipolytica lipase 2 (LIP2) gene was cloned into S. cerevisiae expression vectors and used to generate S. cerevisiae strains that secrete active Lip2 lipase (Lip2p) enzyme into the growth media. Specifically, LIP2 expression was driven by the S. cerevisiae PEX11 promoter, which maintains basal transgene expression levels in the presence of sugars in the culture medium but is rapidly
upregulated by fatty acids. Northern blotting, lipase enzyme activity assays, and gas chromatographic measurements of cellular
fatty acid composition after lipid feeding all confirmed that cells transformed with the PEX11 promoter–LIP2 construct were responsive to lipids in the media, i.e., cells expressing LIP2 responded rapidly to either free fatty acids or TAGs and accumulated high levels of the corresponding fatty acids in intracellular
lipids. These data provided evidence of the creation of a self-regulating positive control feedback loop that allows the cells
to upregulate Lip2p production only when lipids are present in the media. Regulated, autonomous production of extracellular
lipase activity is a necessary step towards the generation of yeast strains that can serve as biocatalysts for conversion
of low-value lipids to value-added TAGs and other novel lipid products. 相似文献
19.
Nouioui I Ghodhbane-Gtari F Beauchemin NJ Tisa LS Gtari M 《Antonie van Leeuwenhoek》2011,100(4):579-587
To construct an evolutionary hypothesis for the genus Frankia, gyrB (encoding gyrase B), nifH (encoding nitrogenase reductase) and glnII (encoding glutamine synthetase II) gene sequences were considered for 38 strains. The overall clustering pattern among
Frankia strains based on the three analyzed sequences varied among themselves and with the previously established 16S rRNA gene phylogeny
and they did not reliably reflect clear evolution of the four discerned Frankia clusters (1, 2, 3 and 4). Based on concatenated gyrB, nifH and glnII, robust phylogenetic trees were observed with the three treeing methods (Maximum Likelihood, Parsimony and Neighbor-Joining)
and supported by strong bootstrap and posterior probability values (>75%) for overall branching. Cluster 4 (non-infective
and/or non-nitrogen-fixing Frankia) was positioned at a deeper branch followed by cluster 3 (Rhamnaceae and Elaeagnaceae infective Frankia), while cluster 2 represents uncultured Frankia microsymbionts of the Coriariaceae, Datiscaceae, Rosaceae and of Ceanothus sp. (Rhamnaceae); Cluster 1 (Betulaceae, Myricaceae and Casuarinaceae infective Frankia) appears to have diverged more recently. The present study demonstrates the utility of phylogenetic analyses based upon concatenated
gyrB, nifH and glnII sequences to help resolve previously unresolved or poorly resolved nodes and will aid in describing species among the genus
Frankia. 相似文献
20.
Marta O. Domingos Keyde C. M. Melo Irys Viana Neves Cristiane M. Mota Rita C. Ruiz Bruna S. Melo Raphael C. Lima Denise S. P. Q. Horton Monamaris M. Borges Marcia R. Franzolin 《Journal of microbiology (Seoul, Korea)》2016,54(11):745-752
Using clonal phylogenetic methods, it has been demonstrated that O111:H25 atypical enteropathogenic E. coli (aEPEC) strains belong to distinct clones, suggesting the possibility that their ability to interact with different hosts and abiotic surfaces can vary from one clone to another. Accordingly, the ability of O111:H25 aEPEC strains derived from human, cat and dogs to adhere to epithelial cells has been investigated, along with their ability to interact with macrophages and to form biofilms on polystyrene, a polymer used to make biomedical devices. The results demonstrated that all the strains analyzed were able to adhere to, and to form pedestals on, epithelial cells, mechanisms used by E. coli to become strongly attached to the host. The strains also show a Localized-Adherence-Like (LAL) pattern of adhesion on HEp-2 cells, a behavior associated with acute infantile diarrhea. In addition, the O111:H25 aEPEC strains derived either from human or domestic animals were able to form long filaments, a phenomenon used by some bacteria to avoid phagocytosis. O111:H25 aEPEC strains were also encountered inside vacuoles, a characteristic described for several bacterial strains as a way of protecting themselves against the environment. They were also able to induce TNF-α release via two routes, one dependent on TLR-4 and the other dependent on binding of Type I fimbriae. These O111:H25 strains were also able to form biofilms on polystyrene. In summary the results suggest that, regardless of their source (i.e. linked to human origin or otherwise), O111:H25 aEPEC strains carry the potential to cause human disease. 相似文献