Cohesin Protects Genes against γH2AX Induced by DNA Double-Strand Breaks

Chromatin undergoes major remodeling around DNA double-strand breaks (DSB) to promote repair and DNA damage response (DDR) activation. We recently reported a high-resolution map of γH2AX around multiple breaks on the human genome, using a new cell-based DSB inducible system. In an attempt to further characterize the chromatin landscape induced around DSBs, we now report the profile of SMC3, a subunit of the cohesin complex, previously characterized as required for repair by homologous recombination. We found that recruitment of cohesin is moderate and restricted to the immediate vicinity of DSBs in human cells. In addition, we show that cohesin controls γH2AX distribution within domains. Indeed, as we reported previously for transcription, cohesin binding antagonizes γH2AX spreading. Remarkably, depletion of cohesin leads to an increase of γH2AX at cohesin-bound genes, associated with a decrease in their expression level after DSB induction. We propose that, in agreement with their function in chromosome architecture, cohesin could also help to isolate active genes from some chromatin remodelling and modifications such as the ones that occur when a DSB is detected on the genome

Halogens as tracers of protosolar nebula material in comet 67P/Churyumov–Gerasimenko

We report the first in situ detection of halogens in a cometary coma, that of 67P/ChuryumovGerasimenko. Neutral gas mass spectra collected by the European Space Agency’s Rosetta spacecraft during four periods of interest from the first comet encounter up to perihelion indicate that the main halogen-bearing compounds are HF, HCl and HBr. The bulk elemental abundances relative to oxygen are ~8.9 × 10⁻⁵ for F/O, ~1.2 × 10⁻⁴ for Cl/O and ~2.5 × 10⁻⁶ for Br/O, for the volatile fraction of the comet. The cometary isotopic ratios for ³⁷Cl/³⁵Cl and ⁸¹Br/⁷⁹Br match the Solar system values within the error margins. The observations point to an origin of the hydrogen halides in molecular cloud chemistry, with frozen hydrogen halides on dust grains, and a subsequent incorporation into comets as the cloud condensed and the Solar system formed

The chromatin remodeler p400 ATPase facilitates Rad51-mediated repair of DNA double-strand breaks

DNA damage signaling and repair take place in a chromatin context. Consequently, chromatin-modifying enzymes, including adenosine triphosphate–dependent chromatin remodeling enzymes, play an important role in the management of DNA double-strand breaks (DSBs). Here, we show that the p400 ATPase is required for DNA repair by homologous recombination (HR). Indeed, although p400 is not required for DNA damage signaling, DNA DSB repair is defective in the absence of p400. We demonstrate that p400 is important for HR-dependent processes, such as recruitment of Rad51 to DSB (a key component of HR), homology-directed repair, and survival after DNA damage. Strikingly, p400 and Rad51 are present in the same complex and both favor chromatin remodeling around DSBs. Altogether, our data provide a direct molecular link between Rad51 and a chromatin remodeling enzyme involved in chromatin decompaction around DNA DSBs

Synthesis and characterization of apatite structure sputter deposited coatings dedicated to intermediate temperature solid oxide fuel cells

La-Si metallic coatings with La/Si ratios between 1.55 and 1.66 were synthesized by Direct Current Magnetron Sputtering of lanthanum and silicon targets in pure argon atmosphere. After the deposition stage, the ceramic apatite-structure coatings were obtained by thermal oxidation in air for 2 hours at 1173 K. The structural and chemical features of these films have been assessed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). The electrical properties were determined by Complex Impedance Spectroscopy in planar configuration. The films with near apatite structure La/Si atomic ratio in range of La10Si6027 and La9.33Si6026 deposited on different substrates were initially amorphous. After thermal oxidation at 1173 K in air, the coating crystallised under the expected apatite structure. SEM observation revealed that the film compactness and thickness increased after thermal oxidation. The film adhesion on SOFCs material is guaranteed if the anode support was not reduced before the deposition stage. A specific method was performed to measure the electrical conductivity, i.e. to determine the ionic conductivity of the film: it uses the four-point probe technique combined with ac impedance spectroscopy. The good agreement between measurements performed in this work (Ea = 0.75 eV, 973 K, = 3-4 10−3 S*cm−1) and literature data allows concluding that deposited layers are of good quality and should be used as electrolyte in an Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC)

Synthesis and characterization of apatite structure sputter deposited coatings dedicated to intermediate temperature solid oxide fuel cells

La-Si metallic coatings with La/Si ratios between 1.55 and 1.66 were synthesized by Direct Current Magnetron Sputtering of lanthanum and silicon targets in pure argon atmosphere. After the deposition stage, the ceramic apatite-structure coatings were obtained by thermal oxidation in air for 2 hours at 1173 K. The structural and chemical features of these films have been assessed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). The electrical properties were determined by Complex Impedance Spectroscopy in planar configuration. The films with near apatite structure La/Si atomic ratio in range of La10Si6027 and La9.33Si6026 deposited on different substrates were initially amorphous. After thermal oxidation at 1173 K in air, the coating crystallised under the expected apatite structure. SEM observation revealed that the film compactness and thickness increased after thermal oxidation. The film adhesion on SOFCs material is guaranteed if the anode support was not reduced before the deposition stage. A specific method was performed to measure the electrical conductivity, i.e. to determine the ionic conductivity of the film: it uses the four-point probe technique combined with ac impedance spectroscopy. The good agreement between measurements performed in this work (Ea = 0.75 eV, 973 K, = 3-4 10−3 S*cm−1) and literature data allows concluding that deposited layers are of good quality and should be used as electrolyte in an Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC)

Effect of total pressure on La 2 NiO 4 coatings deposited by reactive magnetron sputtering using plasma emission monitoring

This work focuses on the structural, microstructural, electrical and electrochemical characterization of La–Ni–O coatings deposited by reactive magnetron sputtering under different argon partial pressures. Deposition was driven by Plasma Emission Monitoring system (PEM) which allows high deposition rate. For each pressure, the optimal regulation setpoint for lanthanum oxide deposition is determined and then the current dissipated on the nickel target is adjusted to obtain the convenient La/Ni ratio to achieve the K2NiF4 structure. After an appropriate annealing treatment, coatings crystallize in the desired structure with more or less impurities. Increasing the device's pressure from 0.4 to 4.8Pa produces more porous samples with different microstructures. Then, a coating with porosity gradient was built by using these four different total pressures. Its electrical performances were tested and allowed its utilization as cathode layer in intermediate temperature-solid oxide fuel cell (IT-SOFC). This modified architecture cathode allows better performances (71mW·cm−2) than dense cathode produced by the same technique (51mW·cm−2)

Fe-based bimetallic catalysts: evidencing the interplay between the two metals using in situ/operando XAS and chemometrics

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