The Peptidyl Prolyl Isomerase Rrd1 Regulates the Elongation of RNA Polymerase II during Transcriptional Stresses

Rapamycin is an anticancer agent and immunosuppressant that acts by inhibiting the TOR signaling pathway. In yeast, rapamycin mediates a profound transcriptional response for which the RRD1 gene is required. To further investigate this connection, we performed genome-wide location analysis of RNA polymerase II (RNAPII) and Rrd1 in response to rapamycin and found that Rrd1 colocalizes with RNAPII on actively transcribed genes and that both are recruited to rapamycin responsive genes. Strikingly, when Rrd1 is lacking, RNAPII remains inappropriately associated to ribosomal genes and fails to be recruited to rapamycin responsive genes. This occurs independently of TATA box binding protein recruitment but involves the modulation of the phosphorylation status of RNAPII CTD by Rrd1. Further, we demonstrate that Rrd1 is also involved in various other transcriptional stress responses besides rapamycin. We propose that Rrd1 is a novel transcription elongation factor that fine-tunes the transcriptional stress response of RNAPII

Curcuminoid Binding to Embryonal Carcinoma Cells: Reductive Metabolism, Induction of Apoptosis, Senescence, and Inhibition of Cell Proliferation

Curcumin preparations typically contain a mixture of polyphenols, collectively referred to as curcuminoids. In addition to the primary component curcumin, they also contain smaller amounts of the co-extracted derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids can be differentially solubilized in serum, which allows for the systematic analysis of concentration-dependent cellular binding, biological effects, and metabolism. Technical grade curcumin was solubilized in fetal calf serum by two alternative methods yielding saturated preparations containing either predominantly curcumin (60%) or bisdemethoxycurcumin (55%). Continual exposure of NT2/D1 cells for 4–6 days to either preparation in cell culture media reduced cell division (1–5 µM), induced senescence (6–7 µM) or comprehensive cell death (8–10 µM) in a concentration-dependent manner. Some of these effects could also be elicited in cells transiently exposed to higher concentrations of curcuminoids (47 µM) for 0.5–4 h. Curcuminoids induced apoptosis by generalized activation of caspases but without nucleosomal fragmentation. The equilibrium binding of serum-solubilized curcuminoids to NT2/D1 cells incubated with increasing amounts of curcuminoid-saturated serum occurred with apparent overall dissociation constants in the 6–10 µM range. However, the presence of excess free serum decreased cellular binding in a hyperbolic manner. Cellular binding was overwhelmingly associated with membrane fractions and bound curcuminoids were metabolized in NT2/D1 cells via a previously unidentified reduction pathway. Both the binding affinities for curcuminoids and their reductive metabolic pathways varied in other cell lines. These results suggest that curcuminoids interact with cellular binding sites, thereby activating signal transduction pathways that initiate a variety of biological responses. The dose-dependent effects of these responses further imply that distinct cellular pathways are sequentially activated and that this activation is dependent on the affinity of curcuminoids for the respective binding sites. Defined serum-solubilized curcuminoids used in cell culture media are thus suitable for further investigating the differential activation of signal transduction pathways

Local activation of light-induced degradation in co-doped boron-phosphorus silicon: Evidence of defect diffusion phenomena

International audienceThis study is interested in the local activation of Light-induced degradation (LID) defect in highly co-doped silicon wafers with boron and phosphorus. For this purpose, the experiments are focused on measuring the minority carrier lifetime before and after LID activation via a mapping technique. The LID defect density exhibits a Gaussian distribution centered on the excitation point of the laser beam; the intensity of the Gaussian distribution of the LID defect varies with the concentration of the co-dopants. The lifetime of the minority carriers decreases in all-silicon sample regions, while the excitation laser beam focuses on an area of approximately one mm2. This observation indicates that LID defects are activated even in the unexcited areas of silicon wafers, suggesting a LID diffusion phenomenon from the laser excitation point to the whole silicon wafer. We deduce that a high phosphorus doping level in silicon wafers leads to a significant reduction in the LID effect

Minority carrier lifetime enhancement in multicrystalline silicon

In this work a new passivation method is proposed for multicrystalline silicon wafers. This method combines the use of porous silicon (PS) and silicon nitride (SiN) coating. SiN thin film is deposited on porous silicon by the plasma-enhanced chemical vapor deposition (PECVD) technique at low temperature and investigated as a passivating and an antireflection coating. We demonstrate that silicon nitride-covered porous silicon is capable of giving an outstanding surface passivation quality on mc-Si. PS-SiN passivation on mc-Si leads to an effective minority carrier lifetime of 100 μs, which is among the highest lifetimes attained on this kind of material. This high effective lifetime results not only from the excellent degree of surface passivation but also from the grain boundaries and bulk passivation. The surface reflectivity was dramatically reduced from 27% for untreated Si wafer to about 5% after PS-SiN coating in the 400–1100 nm wavelength range

Analysis of DNA methylation patterns associated with drought stress response in faba bean (Vicia faba L.) using methylation-sensitive amplification polymorphism (MSAP)

The effects of drought on water relations, gas exchanges and epigenetic alterations were studied in two faba bean (Vicia faba L.) genotypes with contrasting levels of drought tolerance. The drought-tolerant Bachar genotype was less affected by water deficit in comparison with the drought-sensitive F177 in terms of photosynthetic function and water status in plants as indicated by less reduction in net photosynthesis (A), transpiration rate (E), stomatal conductance (gs) and relative water content (RWC). In this study, the methylation-sensitive amplification polymorphism (MSAP) technique was used to profile the DNA methylation patterns of Bachar and F177 under drought and control conditions. Overall, the amount of methylation was higher in leaves than in roots and the contribution of fully methylated loci was always higher than that of hemimethylated loci. Under control and drought treatment, the total methylation level in leaf tissues was 37.43% and 30.62% in Bachar, 41.23% and 38.16% in F177, indicating a decrease of 6.81% and 3.07% in Bachar and F177 respectively, due to drought exposure. The results revealed that DNA methylation in root tissues was decreased by 3.63% (from 23.43% to 19.80%) in Bachar and increased by 0.66% (from 16.53% to 17.19%) in F177 under drought stress. Differentially displayed DNA fragments in MSAP profiles were cloned and sequenced. A sequence analysis identified six potentially drought stress-related differentially methylated regions (DMRs). Five of these have high homology to previously identified or putative proteins found in other plants, including lipoxygenase (LOX), calcium-dependent protein kinase (CDPK), ABC transporter family (ABC), glycosyl hydrolase (GH) and phosphoenolpyruvate carboxylase (PEPC) and were chosen for further characterization. Quantitative reverse transcription PCR analysis revealed that VfLOX, VfCDPK, VfABC and VfGH varied under drought stress; the expression level of these studied genes was higher in Bachar than in F177. This could suggest their possible role in faba bean drought stress tolerance. Overall, the genome-wide epigenetic changes are probably an important regulatory mechanism for faba bean response to drought and as well to other environmental stresses. © 2017 Elsevier B.V

Influence of silver doping on physical properties of sprayed In2S3 films for solar cells application

A set of silver-doped indium sulphide (In2S3:Ag) thin films were deposited by spray pyrolysis technique, at 350 degrees C, to analyze the effects of the Ag doping on the physical properties of the films. Within the limits of the analyzed dopant concentration, X-ray diffraction (XRD) revealed the polycrystalline nature of the films, crystalizing in the beta-In2S3 cubic phase, regardless the level of doping. Both XRD and Raman spectroscopy confirmed the absence of secondary phases. Optical absorption spectra evidenced that the films are opaque to ultraviolet radiation, but transparent in visible and near infrared regions of the electromagnetic spectrum. According to absorption and extinction coefficients variations, the films are smooth and homogeneous. The forbidden bandgap (E-g) increases with increasing Ag concentration. Photoluminescence measurements reveal that the films exhibit seven emissions related to In2S3 defects. The films are semiconductor and the transport phenomena are assisted via small polaron hopping. The photovoltaic effect in Ag/In2S3(n)/Si(p)/Ag is confirmed by I-V characterization in dark and under illumination.This research was partly supported by the projects HP-NANOBIO Project PID2019-111163RB-100, granted by Spanich Ministry of Science, and Project CIVP18A3940, granted by Fundación Ramón Areces, Spain. CVV thanks Xunta de Galicia (Spain) for the AEMAT (ED431E-2018/08) Strategic Partnership and the use of RIAIDT-USC analytical facilities. CVV belongs to the Galician Competitive Research Group ED431C-2017/22, co-funded by FEDER. Part of this work was also supported by the Portuguese Foundation for Science and Technology (FCT) in the frame work of the Strategic Funding UIDB/04650/2020