Site-directed mutagenesis of conserved inverted repeat sequences in the xylanase C promoter region from Streptomyces sp EC3

Streptomyces sp. EC3, a strain which was originally isolated from cattle manure compost, was shown to possess a strong xylanolytic activity. One of the genes responsible for this activity, xlnC, encodes a secreted xylanase. In the native strain, as in the heterologous host S. lividans, expression of xlnC was detectable in the presence of xylan but not in the presence of glucose. Induction by xylan was shown to take place at the transcriptional level. The transcriptional start site of xlnC was mapped and likely -35 (5'-TTGACA-3') and -10 (5'-GAGAAC-3') motifs were identified. In order to localise putative conserved regulatory sequences, the promoter regions of xylanase-encoding genes from various Streptomyces species were aligned. This alignment revealed the existence of three sets of quite well conserved palindromic AT rich sequences called boxes 1, 2 and 3. Box 3 (5'-CGAAA N TTTCG-3') is the farthest away from the promoter region (150-200 bp). A shorter version of this palindrome (5'-GAAA NN TTTC-3') or (5'-CGAAA-3') constitutes box 1, which is located just upstream of the putative -35 promoter sequence. Box 2, located 5-7 bp upstream of box 1, comprises a shorter palindrome than box 3, with inverted polarity [5'-(G/C)TTTC (N) GAAA(G/C)-3']. The putative regulatory role of the conserved inverted repeats in boxes 2 and 3 in the promoter region of the xlnC gene from Streptomyces sp. EC3, was assessed. These boxes were modified by site-directed mutagenesis, and the mutant promoter regions, as well as the wild-type promoter region, were separately fused to a beta-lactamase reporter gene. Analysis of the expression patterns of these fusions in cultures grown in the presence of glucose, xylan or both carbon sources demonstrated that these motifs were cis -acting negative regulatory elements, each playing a specific role in the regulation of xlnC expression. Box 3 was shown to be critical for the establishment of repression of xlnC expression by glucose, whereas box 2 was shown to play an important role in the induction of xlnC expression by xylan.Peer reviewe

Raï, norme sociale et référence religieuse

Raï, norme sociale et référence religieuseII a été souvent répété que le Raï vantait les plaisirs de l'alcool et de l'amour libre. Cela ne signifierait rien si l'on ne montrait comment ces thèmes, et d'autres, s'articulent avec le rappel des normes, notamment religieuses.Le spleen inhérent au Raï doit beaucoup de sa force d'expression à cet état psychologique du « porte-à-faux » religieux. La chanson raï présente sans fausse pudeur les contradictions entre pulsions et contraintes, entre désirs individuels et nonnes socioreligieuses, entre idéologies concurrentes. Comme l'indique le nom du genre (Raï signifie « opinion », « libre choix »), l'être humain est libre, non seulement de son choix mais aussi de ne pas choisir et de tenter de concilier l'inconciliable. Ce bricolage existentiel, ce surgissemcnt funambulesque de l'individuel se fait bien souvent par la manipulation du réfèrent religieux.Mots clés : Virolle, chanson, amour, marginalité, norme, religion, femmeRaï, Social Norm and Religious ReferenceOne usually hears that Raï praises alcohol and " free love ". That wouln't mean anything if one didn't see how thoses topics and other ones, grow by reference to social rules, especially religious norms.The quality of Raï spleen depends, in part, on this psychological position of religious " overhang ". The songs of Raï present candidly the contradiction between impulses and constraints, between personnal desires and socio-religious norms, between competing ideologies. As the word " Raï " shows (it means " opinion ", " free choice "), the human beeing is free, free with his choices, but also with not choosing anything and trying to manage the irreconcilable. Such an existential do-it-yourself, such a tight-rope uprise of individuality often happens through the manipulation of the religious referent.Key words : Virolle, song, love, marginality, norm, religion, woma

Divination

Des ouvrages médiévaux de géographes ou d’historiens arabes apportent des informations sur certaines pratiques divinatoires des Berbères de l’époque (Lewicki, 1965 ; Kenaud 1943). Ces témoignages, complétés par de rares sources plus anciennes, permettent de mettre en perspective les données relativement abondantes de l’ethnographie et de saisir, diachroniquement, quelques traits de l’organisation par la culture berbère de ce secteur du sacré – au demeurant commun, bien que multiforme, à toute..

Divination

Des ouvrages médiévaux de géographes ou d’historiens arabes apportent des informations sur certaines pratiques divinatoires des Berbères de l’époque (Lewicki, 1965 ; Kenaud 1943). Ces témoignages, complétés par de rares sources plus anciennes, permettent de mettre en perspective les données relativement abondantes de l’ethnographie et de saisir, diachroniquement, quelques traits de l’organisation par la culture berbère de ce secteur du sacré – au demeurant commun, bien que multiforme, à toute..

Edwardsville Bulletin: December 4, 1995

Quantitative proteomics revealed the nature and cause of the different metabolic features underpinning weak and strong antibiotic producing abilities of two model Streptomyces species. SFEAP 201

ΔNp63 Is Essential for Epidermal Commitment of Embryonic Stem Cells

In vivo studies have demonstrated that p63 plays complex and pivotal roles in pluristratified squamous epithelial development, but its precise function and the nature of the isoform involved remain controversial. Here, we investigate the role of p63 in epithelial differentiation, using an in vitro ES cell model that mimics the early embryonic steps of epidermal development. We show that the ΔNp63 isoform is activated soon after treatment with BMP-4, a morphogen required to commit differentiating ES cells from a neuroectodermal to an ectodermal cell fate. ΔNp63 gene expression remains high during epithelial development. P63 loss of function drastically prevents ectodermal cells to commit to the K5/K14-positive stratified epithelial pathway while gain of function experiments show that ΔNp63 allows this commitment. Interestingly, other epithelial cell fates are not affected, allowing the production of K5/K18-positive epithelial cells. Therefore, our results demonstrate that ΔNp63 may be dispensable for some epithelial differentiation, but is necessary for the commitment of ES cells into K5/K14-positive squamous stratified epithelial cells

Temperature-mediated biosynthesis of the phytotoxin phaseolotoxin by Pseudomonas syringae pv. phaseolicola depends on the autoregulated expression of the phtABC genes

Abstract Pseudomonas syringae pv. phaseolicola produces phaseolotoxin in a temperature dependent manner, being optimally synthesized between 18˚C and 20˚C, while no detectable amounts are present above 28˚C. The Pht cluster, involved in the biosynthesis of phaseolotoxin, contains 23 genes that are organized in five transcriptional units. The function of most of the genes from the Pht cluster is still unknown and little information about the regulatory circuitry leading to expression of these genes has been reported. The purpose of the present study was to investigate the participation of pht genes in the regulation of the operons coded into the Pht cluster. We conducted Northern blot, uidA fusions and reverse transcription-PCR assays of pht genes in several mutants unable to produce phaseolotoxin. This allowed us to determine that, in P. syringae pv. phaseolicola NPS3121, genes phtABC are essential to prevent their own expression at 28˚C, a temperature at which no detectable amounts of the toxin are present. We obtained evidence that the phtABC genes also participate in the regulation of the phtD, phtM and phtL operons. According to our results, we propose that PhtABC and other Pht product activities could be involved in the synthesis of the sulfodiaminophosphinyl moiety of phaseolotoxin, which indirectly could be involved in the transcriptional regulation of the phtA operon

On the dynamics of the adenylate energy system: homeorhesis vs homeostasis.

Biochemical energy is the fundamental element that maintains both the adequate turnover of the biomolecular structures and the functional metabolic viability of unicellular organisms. The levels of ATP, ADP and AMP reflect roughly the energetic status of the cell, and a precise ratio relating them was proposed by Atkinson as the adenylate energy charge (AEC). Under growth-phase conditions, cells maintain the AEC within narrow physiological values, despite extremely large fluctuations in the adenine nucleotides concentration. Intensive experimental studies have shown that these AEC values are preserved in a wide variety of organisms, both eukaryotes and prokaryotes. Here, to understand some of the functional elements involved in the cellular energy status, we present a computational model conformed by some key essential parts of the adenylate energy system. Specifically, we have considered (I) the main synthesis process of ATP from ADP, (II) the main catalyzed phosphotransfer reaction for interconversion of ATP, ADP and AMP, (III) the enzymatic hydrolysis of ATP yielding ADP, and (IV) the enzymatic hydrolysis of ATP providing AMP. This leads to a dynamic metabolic model (with the form of a delayed differential system) in which the enzymatic rate equations and all the physiological kinetic parameters have been explicitly considered and experimentally tested in vitro. Our central hypothesis is that cells are characterized by changing energy dynamics (homeorhesis). The results show that the AEC presents stable transitions between steady states and periodic oscillations and, in agreement with experimental data these oscillations range within the narrow AEC window. Furthermore, the model shows sustained oscillations in the Gibbs free energy and in the total nucleotide pool. The present study provides a step forward towards the understanding of the fundamental principles and quantitative laws governing the adenylate energy system, which is a fundamental element for unveiling the dynamics of cellular life