Heat shock response in yeast involves changes in both transcription rates and mRNA stabilities

We have analyzed the heat stress response in the yeast Saccharomyces cerevisiae by determining mRNA levels and transcription rates for the whole transcriptome after a shift from 25uC to 37uC. Using an established mathematical algorithm, theoretical mRNA decay rates have also been calculated from the experimental data. We have verified the mathematical predictions for selected genes by determining their mRNA decay rates at different times during heat stress response using the regulatable tetO promoter. This study indicates that the yeast response to heat shock is not only due to changes in transcription rates, but also to changes in the mRNA stabilities. mRNA stability is affected in 62% of the yeast genes and it is particularly important in shaping the mRNA profile of the genes belonging to the environmental stress response. In most cases, changes in transcription rates and mRNA stabilities are homodirectional for both parameters, although some interesting cases of antagonist behavior are found. The statistical analysis of gene targets and sequence motifs within the clusters of genes with similar behaviors shows that both transcriptional and post-transcriptional regulons apparently contribute to the general heat stress response by means of transcriptional factors and RNA binding proteins.

Grx5 is a mitochondrial glutaredoxin required for the activity of iron/sulfur enzymes

Yeast cells contain a family of three monothiol glutaredoxins: Grx3, 4, and 5. Absence of Grx5 leads to constitutive oxidative damage, exacerbating that caused by external oxidants. Phenotypic defects associated with the absence of Grx5 are suppressed by overexpression ofSSQ1 and ISA2, two genes involved in the synthesis and assembly of iron/sulfur clusters into proteins. Grx5 localizes at the mitochondrial matrix, like other proteins involved in the synthesis of these clusters, and the mature form lacks the first 29 amino acids of the translation product. Absence of Grx5 causes: 1) iron accumulation in the cell, which in turn could promote oxidative damage, and 2) inactivation of enzymes requiring iron/sulfur clusters for their activity. Reduction of iron levels in grx5 null mutants does not restore the activity of iron/sulfur enzymes, and cell growth defects are not suppressed in anaerobiosis or in the presence of disulfide reductants. Hence, Grx5 forms part of the mitochondrial machinery involved in the synthesis and assembly of iron/sulfur centers.

An activator/repressor dual system allows tight tetracycline-regulated gene expression in budding yeast

We have developed an activator/repressor expression system for budding yeast in which tetracyclines control in opposite ways the ability of tetR-based activator and repressor molecules to bind tetO promoters. This combination allows tight expression of tetO-driven genes, both in a direct (tetracycline-repressible) and reverse (tetracycline-inducible) dual system. Ssn6 and Tup1, that are components of a general repressor complex in yeast, have been tested for their repressing properties in the dual system, using lacZ and CLN2 as reporter genes. Ssn6 gives better results and allows complete switching-off of the regulated genes, although increasing the levels of the Tup1-based repressor by expressing it from a stronger promoter improves repressing efficiency of the latter. Effector-mediated shifts between expression and non-expression conditions are rapid. The dual system here described may be useful for the functional analysis of essential genes whose conditional expression can be tightly controlled by tetracyclines.

Evolution and cellular function of monothiol glutaredoxins: involvement in iron-sulphur cluster assembly

A number of bacterial species, mostly proteobacteria, possess monothiol glutaredoxins homologous to the Saccharomyces cerevisiae mitochondrial protein Grx5, which is involved in iron–sulphur cluster synthesis. Phylogenetic profiling is used to predict that bacterial monothiol glutaredoxins also participate in the iron–sulphur cluster (ISC) assembly machinery, because their phylogenetic profiles are similar to the profiles of the bacterial homologues of yeast ISC proteins. High evolutionary cooccurrence is observed between the Grx5 homologues and the homologues of the Yah1 ferredoxin, the scaffold proteins Isa1 and Isa2, the frataxin protein Yfh1 and the Nfu1 protein. This suggests that a specific functional interaction exists between these ISC machinery proteins. Physical interaction analyses using low-definition protein docking predict the formation of strong and specific complexes between Grx5 and several components of the yeast ISC machinery. Two-hybrid analysis has confirmed the in vivo interaction between Grx5 and Isa1. Sequence comparison techniques and cladistics indicate that the other two monothiol glutaredoxins of S. cerevisiae, Grx3 and Grx4, have evolved from the fusion of a thioredoxin gene with a monothiol glutaredoxin gene early in the eukaryotic lineage, leading to differential functional specialization. While bacteria do not contain these chimaeric glutaredoxins, in many eukaryotic species Grx5 and Grx3/4-type monothiol glutaredoxins coexist in the cell.

Glutaredoxins Grx3 and Grx4 regulate nuclear localisation of Aft1 and the oxidative stress response in Saccharomyces cerevisiae

Grx3 and Grx4, two monothiol glutaredoxins of Saccharomyces cerevisiae, regulate Aft1 nuclear localisation. We provide evidence of a negative regulation of Aft1 activity by Grx3 and Grx4. The Grx domain of both proteins played an important role in Aft1 translocation to the cytoplasm. This function was not, however, dependent on the availability of iron. Here we demonstrate that Grx3, Grx4 and Aft1 interact each other both in vivo and in vitro, which suggests the existence of a functional protein complex. Interestingly, each interaction occurred independently on the third member of the complex. The absence of both Grx3 and Grx4 induced a clear enrichment of G1 cells in asynchronous cultures, a slow growth phenotype, the accumulation of intracellular iron and a constitutive activation of the genes regulated by Aft1. The grx3grx4 double mutant was highly sensitive to the oxidising agents hydrogen peroxide and t-butylhydroperoxide but not to diamide. The phenotypes of the double mutant grx3grx4 characterised in this study were mainly mediated by the Aft1 function, suggesting that grx3grx4 could be a suitable cellular model for studying endogenous oxidative stress induced by deregulation of the iron homeostasis. However, our results also suggest that Grx3 and Grx4 might play additional roles in the oxidative stress response through proteins other than Aft1.

Lyotard y La condició postmoderna, Vint-i-cinc anys després

L"any 1979 Jean-François Lyotard (1924-1998) publicava a París La condition postmoderne. Rapport sur le savoir, editat per Les Éditions de Minuit, obra en què es retratava l"home postmodern i que amb el pas dels anys s"ha convertit en una mena de clàssic del pensament contemporani. La tesi de fons del llibre -una obra encarregada per les autoritats del Quebec- és ben coneguda: el saber canvia d"estatut al mateix temps que les societats entren en l"era anomenada postindustrial, segons havien anunciat Daniel Bell i Alain Touraine. Per tant, la qüestió del saber en aquesta època postindustrial -que a grans trets coincideix amb un esperit d"època (Zeitgeist) que es pot identifi car amb la postmodernitat- cal situar-la en la perspectiva de les societats industrials avançades.

La escoba y el caballo: algunas reflexiones sobre la humanidad del juego

Starting from the premise that the term"play" can mean practically anything, the author reflects on the topic of play using the concepts of freedom, play community, exhibition and simulation. Play is not an exclusively human activity. However, there is a human way of playing, which has been the subject of debate throughout the history of thought. The human aspects of play could be consid-ered a demonstration of freedom through the acceptance of rules.

Neuronal activity controls the antagonistic between PGC-1α and SMRT in regulating antioxidant defences

Transcriptional coactivators and corepressors often have multiple targets and can have opposing actions on transcription and downstream physiological events. The coactivator peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α is under-expressed in Huntington's disease and is a regulator of antioxidant defenses and mitochondrial biogenesis. We show that in primary cortical neurons, expression of PGC-1α strongly promotes resistance to excitotoxic and oxidative stress in a cell autonomous manner, whereas knockdown increases sensitivity. In contrast, the transcriptional corepressor silencing mediator of retinoic acid and thyroid hormone receptors (SMRT) specifically antagonizes PGC-1α-mediated antioxidant effects. The antagonistic balance between PGC-1α and SMRT is upset in favor of PGC-1α by synaptic activity. Synaptic activity triggers nuclear export of SMRT reliant on multiple regions of the protein. Concommitantly, synaptic activity post-translationally enhances the transactivating potential of PGC-1α in a p38-dependent manner, as well as upregulating cyclic-AMP response element binding protein-dependent PGC-1α transcription. Activity-dependent targeting of PGC-1α results in enhanced gene expression mediated by the thyroid hormone receptor, a prototypical transcription factor coactivated by PGC-1α and repressed by SMRT. As a consequence of these events, SMRT is unable to antagonize PGC-1α-mediated resistance to oxidative stress in synaptically active neurons. Thus, PGC-1α and SMRT are antagonistic regulators of neuronal vulnerability to oxidative stress. Further, this coactivatorcorepressor antagonism is regulated by the activity status of the cell, with implications for neuronal viability.

Managing innovations in biotechnology

Estudi de la situació, estratègies i tendències de la gestió de les innovacions en biotecnologia. El projecte es desenvolupa amb participants de Polònia, França, Holanda i Espanya. Per tant, l'anàlisi té una perspectiva internacional, principalment centrada en els països esmentats. L'expliació teòrica contrasta amb un projecte de gestió real en una empresa de biotecnologia, amb les dades i la informació obtinguda en una visitat a una empresa de biotecnologia a Polònia

Apologia de l'optimisme

L'optimisme és una característica humana que presenta diversos graus de manifestació, en funció de cada persona concreta, i que es veu influenciada per la seva situació personal i per l'ambient social. També té una arrel biològica que, com justificaré, té una certa relació amb la capacitat creativa i la llibertat, la qual cosa genera reflexions interessants. Com qualsevol característica mental és conseqüència del funcionament del cervell i hi ha gens que hi influeixen, com per exemple un transportador de la serotonina i un receptor de la dopamina, dos neurotransmissors amb múltiples funcions. Curiosament, aquests gens, junt amb altres gens coneguts, intervenen en la nostra capacitat creativa [...].

Comentario a la STS de 16 de mayo de 2012: Condiciones potestativas, incumplimiento contractual y cláusula resolutoria expresa

Resumen y objeto: Los socios de una Sociedad, en virtud del principio de autonomía de la voluntad, pueden definir a través de una cláusula expresa inserta en un contrato entre socios el tipo de incumplimiento que da lugar a la resolución de las compraventas de participaciones de esa sociedad. Dicha cláusula no puede considerarse como una condición puramente potestativa, dependiente de la exclusiva voluntad del deudor, puesto que está ligada al hecho del incumplimiento.

La Llibertat en relació = La libertad en relación

Aquest monografic és possible gràcies als textos que les seves autores van presentar a la taula rodona "Repensar el que és polític" coordinada per María-Milagros Rivera, en el X Congrés de I'Associació Internacional de Filosòfes, titulat "Passió per la Ilibertat. Acció, passió i política. Debats feministes" celebrat a Barcelona, el 2 d'octubre de 2002, organitzat per Fina Birulés a qui agraïm que ens hagi donat I'oportunitat de publicar-los. Totes les autores posen en el centre el fet que la llibertat neix i es desplega sempre amb un sentit del vincle i, com escriu Diana Sartori,amb el sentit de I'autoritat que autoritza el fer, I'actuar. Aquest és un dels pensaments i de la practica política més fructífera nascuda de la política de les dones que han significat la diferència de ser dona al món

From "being to the self" to "become to be": on development of autonomy construction in nursing students

Objective: To understand nursing student's self-consciousness and his/her autonomy in the discipline of fundamentals of professional care in the context of a liberating pedagogical proposal. Methodology. This qualitative, case-based research in the model of Ludke and André involved 14 students participating in the discipline. Data were collected by non-participatory observation and analysis of documents. Field observation was conducted from March to July 2010 and data were collected according to the proposal of Minayo: pre-analysis, exploration of material and treatment of results. Results. We constructed two thematic units of analysis: from "being to the self" and exercise of "become to be". Conclusion. When nursing students feel more liberty, they have the opportunity to substitute the scary prospect of learning something new material to something that motivates their curiosity and leads them to become more autonomous.