3,914 research outputs found
Global transcript and phenotypic analysis of yeast cells expressing Ssa1, Ssa2, Ssa3 or Ssa4 as sole source of cytosolic Hsp70-Ssa chaperone activity.
BACKGROUND: Cytosolic Hsp70 is a ubiquitous molecular chaperone that is involved in responding to a variety of cellular stresses. A major function of Hsp70 is to prevent the aggregation of denatured proteins by binding to exposed hydrophobic regions and preventing the accumulation of amorphous aggregates. To gain further insight into the functional redundancy and specialisation of the highly homologous yeast Hsp70-Ssa family we expressed each of the individual Ssa proteins as the sole source of Hsp70 in the cell and assessed phenotypic differences in prion propagation and stress resistance. Additionally we also analysed the global gene expression patterns in yeast strains expressing individual Ssa proteins, using microarray and RT-qPCR analysis. RESULTS: We confirm and extend previous studies demonstrating that cells expressing different Hsp70-Ssa isoforms vary in their ability to propagate the yeast [PSI+] prion, with Ssa3 being the most proficient. Of the four Ssa family members the heat inducible isoforms are more proficient in acquiring thermotolerance and we show a greater requirement than was previously thought, for cellular processes in addition to the traditional Hsp104 protein disaggregase machinery, in acquiring such thermotolerance. Cells expressing different Hsp70-Ssa isoforms also display differences in phenotypic response to exposure to cell wall damaging and oxidative stress agents, again with the heat inducible isoforms providing better protection than constitutive isoforms. We assessed global transcriptome profiles for cells expressing individual Hsp70-Ssa isoforms as the sole source of cytosolic Hsp70, and identified a significant difference in cellular gene expression between these strains. Differences in gene expression profiles provide a rationale for some phenotypic differences we observed in this study. We also demonstrate a high degree of correlation between microarray data and RT-qPCR analysis for a selection of genes. CONCLUSIONS: The Hsp70-Ssa family provide both redundant and variant-specific functions within the yeast cell. Yeast cells expressing individual members of the Hsp70-Ssa family as the sole source of Ssa protein display differences in global gene expression profiles. These changes in global gene expression may contribute significantly to the phenotypic differences observed between the Hsp70-Ssa family members
Testing the psychometric properties of Kidscreen-27 with Irish children of low socio-economic status
BACKGROUND: Kidscreen-27 was developed as part of a cross-cultural European Union-funded project to standardise the measurement of children’s health-related quality of life. Yet, research has reported mixed evidence for the hypothesised 5-factor model, and no confirmatory factor analysis (CFA) has been conducted on the instrument with children of low socio-economic status (SES) across Ireland (Northern and Republic). METHOD: The data for this study were collected as part of a clustered randomised controlled trial. A total of 663 (347 male, 315 female) 8–9-year-old children (M = 8.74, SD = .50) of low SES took part. A 5- and modified 7-factor CFA models were specified using the maximum likelihood estimation. A nested Chi-square difference test was conducted to compare the fit of the models. Internal consistency and floor and ceiling effects were also examined. RESULTS: CFA found that the hypothesised 5-factor model was an unacceptable fit. However, the modified 7-factor model was supported. A nested Chi-square difference test confirmed that the fit of the 7-factor model was significantly better than that of the 5-factor model. Internal consistency was unacceptable for just one scale. Ceiling effects were present in all but one of the factors. CONCLUSIONS: Future research should apply the 7-factor model with children of low socio-economic status. Such efforts would help monitor the health status of the population
Towards understanding the gliotoxin detoxification mechanism: in vivo thiomethylation protects yeast from gliotoxin cytotoxicity
Gliotoxin (GT) is a mycotoxin produced by some species of ascomycete fungi including the opportunistic human pathogen Aspergillus fumigatus . In order to produce GT the host organism needs to have evolved a selfprotection mechanism. GT contains a redox-cycling disulfide bridge that is important in mediating toxicity. Recently is has been demonstrated that A. fumigatus possesses a novel thiomethyltransferase protein called GtmA that has the ability to thiomethylate GT in vivo , which aids the organism in regulating GT biosynthesis. It has been suggested that thiomethylation of GT and similar sulfur-containing toxins may play a role in providing self-protection in host organisms. In this work we have engineered Saccharomyces cerevisiae , a GT-naïve organism, to express A. fumigatus GtmA. We demonstrate that GtmA can readily thiomethylate GT in yeast, which results in protection of the organism from exogenous GT. Our work has implications for understanding the evolution of GT self-protection mechanisms in organisms that are GT producers and non-producers
Spectral classification and HR diagram of pre-main sequence stars in NGC6530
Mechanisms involved in the star formation process and in particular the
duration of the different phases of the cloud contraction are not yet fully
understood. Photometric data alone suggest that objects coexist in the young
cluster NGC6530 with ages from ~1 Myr up to 10 Myrs. We want to derive accurate
stellar parameters and, in particular, stellar ages to be able to constrain a
possible age spread in the star-forming region NGC6530. We used low-resolution
spectra taken with VIMOS@VLT and literature spectra of standard stars to derive
spectral types of a subsample of 94 candidate members of this cluster. We
assign spectral types to 86 of the 88 confirmed cluster members and derive
individual reddenings. Our data are better fitted by the anomalous reddening
law with R=5. We confirm the presence of strong differential
reddening in this region. We derive fundamental stellar parameters, such as
effective temperatures, photospheric colors, luminosities, masses, and ages for
78 members, while for the remaining 8 YSOs we cannot determine the interstellar
absorption, since they are likely accretors, and their V-I colors are bluer
than their intrinsic colors. The cluster members studied in this work have
masses between 0.4 and 4 M and ages between 1-2 Myrs and 6-7 Myrs. We
find that the SE region is the most recent site of star formation, while the
older YSOs are loosely clustered in the N and W regions. The presence of two
distint generations of YSOs with different spatial distribution allows us to
conclude that in this region there is an age spread of ~6-7 Myrs. This is
consistent with the scenario of sequential star formation suggested in
literature.Comment: 23 pages, 16 Postscript figures, 5 tables. Accepted for publication
in Astronomy and Astrophysic
RNA-seq reveals the pan-transcriptomic impact of attenuating the gliotoxin self-protection mechanism in Aspergillus fumigatus.
BACKGROUND: Aspergillus fumigatus produces a number of secondary metabolites, one of which, gliotoxin, has been shown to exhibit anti-fungal activity. Thus, A. fumigatus must be able to protect itself against gliotoxin. Indeed one of the genes in the gliotoxin biosynthetic gene cluster in A. fumigatus, gliT, is required for self-protection against the toxin- however the global self-protection mechanism deployed is unclear. RNA-seq was employed to identify genes differentially regulated upon exposure to gliotoxin in A. fumigatus wild-type and A. fumigatus ∆gliT, a strain that is hypersensitive to gliotoxin. RESULTS: Deletion of A. fumigatus gliT resulted in altered expression of 208 genes (log2 fold change of 1.5) when compared to A. fumigatus wild-type, of which 175 genes were up-regulated and 33 genes were down-regulated. Expression of 164 genes was differentially regulated (log2 fold change of 1.5) in A. fumigatus wild-type when exposed to gliotoxin, consisting of 101 genes with up-regulated expression and 63 genes with down-regulated expression. Interestingly, a much larger number of genes, 1700, were found to be differentially regulated (log2 fold change of 1.5) in A. fumigatus ∆gliT when challenged with gliotoxin. These consisted of 508 genes with up-regulated expression, and 1192 genes with down-regulated expression. Functional Catalogue (FunCat) classification of differentially regulated genes revealed an enrichment of genes involved in both primary metabolic functions and secondary metabolism. Specifically, genes involved in gliotoxin biosynthesis, helvolic acid biosynthesis, siderophore-iron transport genes and also nitrogen metabolism genes and ribosome biogenesis genes underwent altered expression. It was confirmed that gliotoxin biosynthesis is induced upon exposure to exogenous gliotoxin, production of unrelated secondary metabolites is attenuated in A. fumigatus ∆gliT, while quantitative proteomic analysis confirmed disrupted translation in A. fumigatus ∆gliT challenged with exogenous gliotoxin. CONCLUSIONS: This study presents the first global investigation of the transcriptional response to exogenous gliotoxin in A. fumigatus wild-type and the hyper-sensitive strain, ∆gliT. Our data highlight the global and extensive affects of exogenous gliotoxin on a sensitive strain devoid of a self-protection mechanism and infer that GliT functionality is required for the optimal biosynthesis of selected secondary metabolites in A. fumigatus
Analysis of galaxy SEDs from far-UV to far-IR with CIGALE: Studying a SINGS test sample
Photometric data of galaxies covering the rest-frame wavelength range from
far-UV to far-IR make it possible to derive galaxy properties with a high
reliability by fitting the attenuated stellar emission and the related dust
emission at the same time. For this purpose we wrote the code CIGALE (Code
Investigating GALaxy Emission) that uses model spectra composed of the Maraston
(or PEGASE) stellar population models, synthetic attenuation functions based on
a modified Calzetti law, spectral line templates, the Dale & Helou dust
emission models, and optional spectral templates of obscured AGN. Depending on
the input redshifts, filter fluxes are computed for the model set and compared
to the galaxy photometry by carrying out a Bayesian-like analysis. CIGALE was
tested by analysing 39 nearby galaxies selected from SINGS. The reliability of
the different model parameters was evaluated by studying the resulting
expectation values and their standard deviations in relation to the input model
grid. Moreover, the influence of the filter set and the quality of photometric
data on the code results was estimated. For up to 17 filters between 0.15 and
160 mum, we find robust results for the mass, star formation rate, effective
age of the stellar population at 4000 A, bolometric luminosity, luminosity
absorbed by dust, and attenuation in the far-UV. A study of the mutual
relations between the reliable properties confirms the dependence of star
formation activity on morphology in the local Universe and indicates a
significant drop in this activity at about 10^11 M_sol towards higher total
stellar masses. The dustiest sample galaxies are present in the same mass
range. [abridged]Comment: 22 pages, 21 figures, accepted for publication in A&
Near-infrared spectroscopy in NGC 7538
The characterisation of the stellar population toward young high-mass
star-forming regions allows to constrain fundamental cluster properties like
distance and age. These are essential when using high-mass clusters as probes
to conduct Galactic studies. NGC 7538 is a star-forming region with an embedded
stellar population only unearthed in the near-infrared. We present the first
near-infrared spectro-photometric study of the candidate high-mass stellar
content in NGC 7538. We obtained H and K spectra of 21 sources with both the
multi-object and long-slit modes of LIRIS at the WHT, and complement these data
with sub-arcsecond JHKs photometry of the region using the imaging mode of the
same instrument. We find a wide variety of objects within the studied stellar
population of NGC 7538. Our results discriminate between a stellar population
associated to the HII region, but not contained within its extent, and several
pockets of more recent star formation. We report the detection of CO bandhead
emission toward several sources as well as other features indicative of a young
stellar nature. We infer a spectro-photometric distance of 2.7+-0.5 kpc, an age
spread in the range 0.5-2.2 Myr and a total mass ~1.7x10^3 Msun for the older
population.Comment: 11 pages, 8 figures, 1 table, accepted by A&
Classical Conformal Blocks and Accessory Parameters from Isomonodromic Deformations
Classical conformal blocks naturally appear in the large central charge limit
of 2D Virasoro conformal blocks. In the correspondence, they
are related to classical bulk actions and are used to calculate entanglement
entropy and geodesic lengths. In this work, we discuss the identification of
classical conformal blocks and the Painlev\'e VI action showing how
isomonodromic deformations naturally appear in this context. We recover the
accessory parameter expansion of Heun's equation from the isomonodromic
-function. We also discuss how the expansion of the
-function leads to a novel approach to calculate the 4-point classical
conformal block.Comment: 32+10 pages, 2 figures; v3: upgraded notation, discussion on moduli
space and monodromies, numerical and analytic checks; v2: added refs, fixed
emai
On the geometric quantization of contact manifolds
Suppose that is a compact contact manifold, and that a compact Lie
group acts on transverse to the contact distribution . In an earlier
paper, we defined a -transversally elliptic Dirac operator \dirac,
constructed using a Hermitian metric and connection on the
symplectic vector bundle , whose equivariant index is
well-defined as a generalized function on , and gave a formula for its
index. By analogy with the geometric quantization of symplectic manifolds, the
-graded Hilbert space Q(M)=\ker \dirac \oplus \ker \dirac^{*}
can be interpreted as the "quantization" of the contact manifold ; the
character of the corresponding virtual -representation is then given by the
equivariant index of \dirac. By defining contact analogues of the algebra of
observables, pre-quantum line bundle and polarization, we further extend the
analogy by giving a contact version of the Kostant-Souriau approach to
quantization, and discussing the extent to which this approach is reproduced by
the index-theoretic method.Comment: 25 pages, references added, several corrections and clarifications
and some reorganization of conten
A Single Aspergillus fumigatus Gene Enables Ergothioneine Biosynthesis and Secretion by Saccharomyces cerevisiae.
The naturally occurring sulphur-containing histidine derivative, ergothioneine (EGT), exhibits potent antioxidant properties and has been proposed to confer human health benefits. Although it is only produced by select fungi and prokaryotes, likely to protect against environmental stress, the GRAS organism Saccharomyces cerevisiae does not produce EGT naturally. Herein, it is demonstrated that the recombinant expression of a single gene, Aspergillus fumigatus egtA, in S. cerevisiae results in EgtA protein presence which unexpectedly confers complete EGT biosynthetic capacity. Both High Performance Liquid Chromatography (HPLC) and LC−mass spectrometry (MS) analysis were deployed to detect and confirm EGT production in S. cerevisiae. The localisation and quantification of the resultant EGT revealed a significantly (p < 0.0001) larger quantity of EGT was extracellularly present in culture supernatants than intracellularly accumulated in 96 h yeast cultures. Methionine addition to cultures improved EGT production. The additional expression of two candidate cysteine desulfurases from A. fumigatus was thought to be required to complete EGT biosynthesis, namely AFUA_2G13295 and AFUA_3G14240, termed egt2a and egt2b in this study. However, the co-expression of egtA and egt2a in S. cerevisiae resulted in a significant decrease in the observed EGT levels (p < 0.05). The AlphaFold prediction of A. fumigatus EgtA 3-Dimensional structure illuminates the bidomain structure of the enzyme and the opposing locations of both active sites. Overall, we clearly show that recombinant S. cerevisiae can biosynthesise and secrete EGT in an EgtA-dependent manner which presents a facile means of producing EGT for biotechnological and biomedical use
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