Gcn5 facilitates Pol II progression, rather than recruitment to nucleosome-depleted stress promoters, in Schizosaccharomyces pombe

In the fission yeast, the MAP kinase Sty1 and the transcription factor Atf1 regulate up to 400 genes in response to environmental signals, and both proteins have been shown to bind to their promoters in a stress-dependent manner. In a genetic search, we have isolated the histone H3 acetyltransferase Gcn5, a component of the SAGA complex, as being essential for oxidative stress survival and activation of those genes. Upon stress, Gcn5 is recruited to promoters and coding sequences of stress genes in a Sty1- and Atf1-dependent manner, causing both an enhanced acetylation of histone H3 and nucleosome eviction. Unexpectedly, recruitment of RNA polymerase II (Pol II) is not impaired in Δgcn5 cells. We show here that stress genes display a 400-bp long nucleosome depleted region upstream of the transcription start site even prior to activation. Stress treatment does not alter promoter nucleosome architecture, but induces eviction of the downstream nucleosomes at stress genes, which is not observed in Δgcn5 cells. We conclude that, while Pol II is recruited to nucleosome-free stress promoters in a transcription factor dependent manner, Gcn5 mediates eviction of nucleosomes positioned downstream of promoters, allowing efficient Pol II progression along the genes.Funding for open access charge: Spanish Ministry of Science and Innovation (BFU2009-06933), PLAN E and FEDER, by the Spanish program Consolider-Ingenio 2010 Grant CSD 2007-0020, and by SGR2009-196 from Generalitat de Catalunya (Spain) (to E.H.). E.H. and J.A. are recipients of an ICREA Academia Award (Generalitat de Catalunya

Promoter nucleosome dynamics regulated by signalling through the CTD code

The phosphorylation of the RNA polymerase II C-terminal domain (CTD) plays a key role in delineating transcribed regions within chromatin by recruiting histone methylases and deacetylases. Using genome-wide nucleosome mapping, we show that CTD S2 phosphorylation controls nucleosome dynamics in the promoter of a subset of 324 genes, including the regulators of cell differentiation ste11 and metabolic adaptation inv1. Mechanistic studies on these genes indicate that during gene activation a local increase of phospho-S2 CTD nearby the promoter impairs the phospho-S5 CTD-dependent recruitment of Set1 and the subsequent recruitment of specific HDACs, which leads to nucleosome depletion and efficient transcription. The early increase of phospho-S2 results from the phosphorylation of the CTD S2 kinase Lsk1 by MAP kinase in response to cellular signalling. The artificial tethering of the Lsk1 kinase at the ste11 promoter is sufficient to activate transcription. Therefore, signalling through the CTD code regulates promoter nucleosomes dynamics.This work was supported by grants BFU2011-28804 and Consolider Ingenio CSD2007-00015 from the Spanish Ministerio de Economía y Competitividad to FA, and grants FRFC 2.4510.10, Credit aux chercheurs 1.5.013.09, MIS F.4523.11, Ceruna and Marie Curie Action to DH. DH is a FNRS Research Associat

Environmental and geometric optimisation of cylindrical drinking water storage tanks

The final publication is available at Springer via http://dx.doi.org/10.1007/s11367-015-0963-yPurpose: Urban water cycle construction processes are an important element to consider when assessing the sustainability of urban areas. The present study focuses on a structural and environmental analysis of cylindrical water tanks. The goal is to optimise cylindrical water tanks from both an environmental (environmental impacts due of life cycle assessment (LCA)) and a geometric perspective (building material quantities for construction purposes depending on the tank characteristics). Methods: A sample of 147 cases was defined based on different positions (buried, superficial and partially buried), dimensions (combinations of heights and radii) and storage capacities (between 100 and 10,000 m3). A structural analysis was conducted for a defined set of cases to determine the quantities of steel and concrete required for its construction. The environmental impacts of the entire life cycle were assessed through a life cycle assessment (LCA). Additionally, environmental standards (the less impactful option for each dimension assessed: geometry, storage capacity and position) defined in the study were applied to realistic cases to evaluate potential environmental savings. Results and discussion: The LCA shows that materials are the main contributor to environmental impacts (more than transport, installation and end of life cycle stages). For this reason, the results of the structural and environmental assessments coincide. Taller water tanks have shown to be less impactful (60 to 70 % less impact for a 10.000-m3 tank). Regarding the position, superficial water tanks have shown to have between 15 and 35 % less impact than buried ones. The environmentally preferred water storage capacity is between 1000 and 2500 m3, being between 20 and 40 % less impact. For instance, an 8000-m3 tank would emit 1040 t of CO2 eq. Applying the environmental standards 170.5 t of CO2 eq could be saved (16 % of the total amount). Conclusions: The results of this study show that among the cases analysed, superficially positioned cylindrical water tanks of 8.5 m in height and of between 1000 and 2500 m3 in storage capacity present fewer impacts. The use of these standards in municipal water tanks construction projects may significantly reduce environmental impacts (10 to 40 %) in all impact categories.Peer Reviewe