Two Distinct Nucleosome Alterations Characterize Chromatin Remodeling at the Saccharomyces cerevisiae ADH2Promoter

Glucose depletion derepresses the Saccharomyces cerevisiae ADH2 gene; this metabolic change is accompanied by chromatin structural modifications in the promoter region. We show that the ADR6/SWI1 gene is not necessary for derepression of the wild type chromosomal ADH2, whereas the transcription factor Adr1p, which regulates several S. cerevisiae functions, plays a major role in driving nucleosome reconfiguration and ADH2 expression. When we tested the effect of individual domains of the regulatory protein Adr1p on the chromatin structure of ADH2, a remodeling consisting of at least two steps was observed. Adr1p derivatives were analyzed in derepressing conditions, showing that the Adr1p DNA binding domain alone causes an alteration in chromatin organization in the absence of transcription. This alteration differs from the remodeling observed in the presence of the Adr1p activation domain when the promoter is transcriptionally active

Borate Minerals and RNA Stability

The abiotic origin of genetic polymers faces two major problems: a prebiotically plausible polymn. mechanism and the maintenance of their polymd. state outside a cellular environment. The stabilizing action of borate on ribose having been reported, the authors have explored the possibility that borate minerals stabilize RNA. Borate itself does not stabilize RNA. The anal. of a large panel of minerals tested in various phys.-chem. conditions shows that in general no protection is exerted on the RNA backbone, with the interesting exception of ludwigite (Mg2Fe3+BO5). Stability is a fundamental property of nucleic polymers and borate is an abundant component of the planet, hence the prebiotic interest of this anal. L'articolo è disponibile sul sito dell'editore: http://www.mdpi.co

Heterochromatin Organization of a Natural Yeast Telomere CHANGES OF NUCLEOSOME DISTRIBUTION DRIVEN BY THE ABSENCE OF Sir3p

We have defined the in vivoheterochromatin structure of the left telomere of Saccharomyces cerevisiae chromosome III (LIII). Analysis of heterochromatin of a single telomere was so far lacking, due to the difficulties intrinsic to the highly repetitive nature of telomeric sequences. In LIII, the terminal (C1–3A)n repetitive sequences are followed by a complete X element and by the single copy Ty5-1 retrotransposon. Both the telosome and the X element exhibit overall resistance to micrococcal nuclease digestion reflecting their tight chromatin structure organization. The X element contains protein complexes and irregularly distributed but well localized nucleosomes. In contrast, a regular array of phased nucleosomes is associated with the promoter region of Ty5-1 and with the more centromere-proximal sequences. The lack of a structural component of yeast telomeres, the SIR3 protein, does not alter the overall tight organization of the X element but causes a nucleosome rearrangement within the promoter region of Ty5-1 and releases Ty5-1 silencing. Thus, Sir3p links the modification of the heterochromatin structure with loss of transcriptional silencing

one step one lane chemical dna sequencing by n methylformamide in the presence of metal ions

We report on a chemical method that allows DNA sequencing by a single reaction. It is based on treatment of 5′-end-labeled DNA with N-methylformamide in the presence of manganese. This method allows the manipulation of samples to be kept to a minimum and consists of a single chemical step that requires about 30 minutes to complete base degradation, phosphodiester bond cleavage and denaturation. Examples of one-treatment, one-lane DNA sequencing of both radioactively and fluorescently 5′-end-labeled DNAs are reported

A global scale scenario for prebiotic chemistry: silica-based self- assembled mineral structures and formamide

The pathway from simple abiotically made organic compounds to the molecular bricks of life, as we know it, is unknown. The most efficient geological abiotic route to organic compounds results from the aqueous dissolution of olivine, a reaction known as serpentinization (Sleep, N.H., et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12818–12822). In addition to molecular hydrogen and a reducing environment, serpentinization reactions lead to high-pH alkaline brines that can become easily enriched in silica. Under these chemical conditions, the formation of self-assembled nanocrystalline mineral composites, namely silica/carbonate biomorphs and metal silicate hydrate (MSH) tubular membranes (silica gardens), is unavoidable (Kellermeier, M., et al. In Methods in Enzymology, Research Methods in Biomineralization Science (De Yoreo, J., Ed.) Vol. 532, pp 225–256, Academic Press, Burlington, MA). The osmotically driven membranous structures have remarkable catalytic properties that could be operating in the reducing organic-rich chemical pot in which they form. Among one-carbon compounds, formamide (NH2CHO) has been shown to trigger the formation of complex prebiotic molecules under mineral-driven catalytic conditions (Saladino, R., et al. (2001) Biorganic & Medicinal Chemistry, 9, 1249–1253), proton irradiation (Saladino, R., et al. (2015) Proc. Natl. Acad. Sci. USA, 112, 2746–2755), and laser-induced dielectric breakdown (Ferus, M., et al. (2015) Proc Natl Acad Sci USA, 112, 657–662). Here, we show that MSH membranes are catalysts for the condensation of NH2CHO, yielding prebiotically relevant compounds, including carboxylic acids, amino acids, and nucleobases. Membranes formed by the reaction of alkaline (pH 12) sodium silicate solutions with MgSO4 and Fe2(SO4)3·9H2O show the highest efficiency, while reactions with CuCl2·2H2O, ZnCl2, FeCl2·4H2O, and MnCl2·4H2O showed lower reactivities. The collections of compounds forming inside and outside the tubular membrane are clearly specific, demonstrating that the mineral self-assembled membranes at the same time create space compartmentalization and selective catalysis of the synthesis of relevant compounds. Rather than requiring odd local conditions, the prebiotic organic chemistry scenario for the origin of life appears to be common at a universal scale and, most probably, earlier than ever thought for our planet.European Research Council under the European Union’s Seventh Framework Programme (FP7/2007−2013)/ERC Grant Agreement 340863Peer reviewe

The role of borosilicate glass in Miller–Urey experiment

The authors thank the European Research Council under the European Union's seventh Framework Program (FP7/2007-2013)/ERC grant agreement no. 340863 and the Spanish "Ministerio de Educacion y Ciencia" for the financial support of the project CGL2016-78971-P, the Italian Space Agency for co-funding the Life in Space project (ASI N. 2019-3-U.0) and MIUR 2017-PNR cod. 2017BMK8JR. This work is supported by the Italian Space Agency (ASI) DC-VUM-2017-034 contratto ASI N. 2019-3-U.0, CUP F86C16000000006 "Vita nello spazioOrigine, presenza, persistenza della vita nello spazio, dalle molecole agli estremofili".We have designed a set of experiments to test the role of borosilicate reactor on the yielding of the Miller–Urey type of experiment. Two experiments were performed in borosilicate flasks, two in a Teflon flask and the third couple in a Teflon flask with pieces of borosilicate submerged in the water. The experiments were performed in CH4, N2, and NH3 atmosphere either buffered at pH 8.7 with NH4Cl or unbuffered solutions at pH ca. 11, at room temperature. The Gas Chromatography-Mass Spectroscopy results show important differences in the yields, the number of products, and molecular weight. In particular, a dipeptide, multi-carbon dicarboxylic acids, PAHs, and a complete panel of biological nucleobases form more efficiently or exclusively in the borosilicate vessel. Our results offer a better explanation of the famous Miller’s experiment showing the efficiency of borosilicate in a triphasic system including water and the reduced Miller–Urey atmosphere.European Research Council (ERC) 340863Spanish Government CGL2016-78971-PAgenzia Spaziale Italiana (ASI) 2019-3-U.0Ministry of Education, Universities and Research (MIUR) 2017BMK8JRAgenzia Spaziale Italiana (ASI) 2019-3-U.0 DC-VUM-2017-034 CUP F86C1600000000

Transaction signature (TSIG) : Una alternativa de seguridad para transferencias de zonas DNS

Desde su creación el Sistema de Nombres de Dominio, ha carecido de un diseño que asegure la comunicación entre las partes que intervienen en el proceso de resolución de nombres. Y dada su condición de sistema público y estructura jerárquica, es que se encuentra expuesto a posibles vectores de “ataque” a lo largo de todo el flujo de datos intercambiado por los componentes (Clientes y Servidores) que lo conforman. Es así que, en el Centro de Investigación y Desarrollo en Informática Aplicada (C.I.D.I.A.) perteneciente a la Universidad Nacional de Salta se formó un equipo de trabajo que se encuentra realizando una investigación aplicada cuyo objetivo es presentar de manera práctica el conjunto de vulnerabilidades presentes en el Sistema de Nombres de Dominio y definir las medidas a implementar para mitigar las mismas. Se detalla a continuación un caso práctico sobre la vulnerabilidad presente en una transferencia de zona y la alternativa TSIG (Transaction Signature) como parte de un conjunto de medidas para dotar de seguridad a los procesos involucrados en tales transferencias.Eje: Arquitectura, Redes y Sistemas OperativosRed de Universidades con Carreras en Informática (RedUNCI