AATF, a novel transcription factor that interacts with Dlk/ZIP kinase and interferes with apoptosis11Accession no. for rat AATF nucleotide sequence at the EMBL GenBank database is RNO238717.

AbstractDlk, also known as ZIP kinase, is a serine/threonine kinase that is tightly associated with nuclear structures. Under certain conditions, which require cytoplasmic localization, Dlk can induce apoptosis. In search for interaction partners that might serve as regulators or targets of this kinase we identified apoptosis antagonizing transcription factor (AATF), a nuclear phosphoprotein of 523 amino acids. The 1.8 kb mRNA seems to be ubiquitously expressed. AATF contains an extremely acidic domain and a putative leucine zipper characteristic of transcription factors. Indeed, a Gal4-BD-AATF fusion protein exhibited strong transactivation activity. Interestingly, AATF interfered with Dlk-induced apoptosis

Narrative-based computational modelling of the Gp130/JAK/STAT signalling pathway.

BACKGROUND: Appropriately formulated quantitative computational models can support researchers in understanding the dynamic behaviour of biological pathways and support hypothesis formulation and selection by "in silico" experimentation. An obstacle to widespread adoption of this approach is the requirement to formulate a biological pathway as machine executable computer code. We have recently proposed a novel, biologically intuitive, narrative-style modelling language for biologists to formulate the pathway which is then automatically translated into an executable format and is, thus, usable for analysis via existing simulation techniques. RESULTS: Here we use a high-level narrative language in designing a computational model of the gp130/JAK/STAT signalling pathway and show that the model reproduces the dynamic behaviour of the pathway derived by biological observation. We then "experiment" on the model by simulation and sensitivity analysis to define those parameters which dominate the dynamic behaviour of the pathway. The model predicts that nuclear compartmentalisation and phosphorylation status of STAT are key determinants of the pathway and that alternative mechanisms of signal attenuation exert their influence on different timescales. CONCLUSION: The described narrative model of the gp130/JAK/STAT pathway represents an interesting case study showing how, by using this approach, researchers can model biological systems without explicitly dealing with formal notations and mathematical expressions (typically used for biochemical modelling), nevertheless being able to obtain simulation and analysis results. We present the model and the sensitivity analysis results we have obtained, that allow us to identify the parameters which are most sensitive to perturbations. The results, which are shown to be in agreement with existing mathematical models of the gp130/JAK/STAT pathway, serve us as a form of validation of the model and of the approach itself

Massively parallel identification of mRNA localization elements in primary cortical neurons

Cells adopt highly polarized shapes and form distinct subcellular compartments in many cases due to the localization of many mRNAs to specific areas, where they are translated into proteins with local functions. This mRNA localization is mediated by specific cis-regulatory elements in mRNAs, commonly called ‘zipcodes’. Although there are hundreds of localized mRNAs, only a few zipcodes have been characterized. Here we describe a novel neuronal zipcode identification protocol (N-zip) that can identify zipcodes across hundreds of 3′ untranslated regions. This approach combines a method of separating the principal subcellular compartments of neurons—cell bodies and neurites—with a massively parallel reporter assay. N-zip identifies the let-7 binding site and (AU)n motif as de novo zipcodes in mouse primary cortical neurons. Our analysis also provides, to our knowledge, the first demonstration of an miRNA affecting mRNA localization and suggests a strategy for detecting many more zipcodes

Abundance estimation of Ixodes ticks (Acari: Ixodidae) on roe deer (Capreolus capreolus)

Despite the importance of roe deer as a host for Ixodes ticks in central Europe, estimates of total tick burden on roe deer are not available to date. We aimed at providing (1) estimates of life stage and sex specific (larvae, nymphs, males and females, hereafter referred to as tick life stages) total Ixodes burden and (2) equations which can be used to predict the total life stage burden by counting the life stage on a selected body area. Within a period of 1½ years, we conducted whole body counts of ticks from 80 hunter-killed roe deer originating from a beech dominated forest area in central Germany. Averaged over the entire study period (winter 2007–summer 2009), the mean tick burden per roe deer was 64.5 (SE ± 10.6). Nymphs were the most numerous tick life stage per roe deer (23.9 ± 3.2), followed by females (21.4 ± 3.5), larvae (10.8 ± 4.2) and males (8.4 ± 1.5). The individual tick burden was highly aggregated (k = 0.46); levels of aggregation were highest in larvae (k = 0.08), followed by males (k = 0.40), females (k = 0.49) and nymphs (k = 0.71). To predict total life stage specific burdens based on counts on selected body parts, we provide linear equations. For estimating larvae abundance on the entire roe deer, counts can be restricted to the front legs. Tick counts restricted to the head are sufficient to estimate total nymph burden and counts on the neck are appropriate for estimating adult ticks (females and males). In order to estimate the combined tick burden, tick counts on the head can be used for extrapolation. The presented linear models are highly significant and explain 84.1, 77.3, 90.5, 91.3, and 65.3% (adjusted R2) of the observed variance, respectively. Thus, these models offer a robust basis for rapid tick abundance assessment. This can be useful for studies aiming at estimating effects of abiotic and biotic factors on tick abundance, modelling tick population dynamics, modelling tick-borne pathogen transmission dynamics or assessing the efficacy of acaricides

Attachment site selection of ticks on roe deer, Capreolus capreolus

The spatio-temporal attachment site patterns of ticks feeding on their hosts can be of significance if co-feeding transmission (i.e. from tick to tick without a systemic infection of the host) of pathogens affects the persistence of a given disease. Using tick infestation data on roe deer, we analysed preferred attachment sites and niche width of Ixodes ticks (larvae, nymphs, males, females) and investigated the degree of inter- and intrastadial aggregation. The different development stages showed rather consistent attachment site patterns and relative narrow feeding site niches. Larvae were mostly found on the head and on the front legs of roe deer, nymphs reached highest densities on the head and highest adult densities were found on the neck of roe deer. The tick stages feeding (larvae, nymphs, females) on roe deer showed high degrees of intrastadial spatial aggregation, whereas males did not. Male ticks showed large feeding site overlap with female ticks. Feeding site overlap between larval-female and larval-nymphal ticks did occur especially during the months May–August on the head and front legs of roe deer and might allow pathogen transmission via co-feeding. Tick density, niche width and niche overlap on roe deer are mainly affected by seasonality, reflecting seasonal activity and abundance patterns of ticks. Since different tick development stages occur spatially and temporally clustered on roe deer, transmission experiments of tick-borne pathogens are urgently needed

Intelligent management of the heat storage tank for production of electricity on demand using CHP units

The paper illustrates the status quo of a research project for the development of a control system enabling CHP units for a demand-oriented electricity production by an intelligent management of the heat storage tank. Thereby the focus of the project is twofold. One is the compensation of the fluctuating power production by the renewable energies solar and wind. Secondly, a reduction of the load on the power grid is intended by a better match of local electricity demand and production. In detail, the general control strategy is outlined, the method utilized for forecasting heat and electricity demand is illustrated as well as a correlation method for the temperature distribution in the heat storage tank based on a Sigmoid function is proposed. Moreover, the simulation model for verification and optimization of the control system and the two field test sites for implementing and testing the system are introduced

Investigations on the role of nuclear export of the transcription factor STAT1 for cytokine-induced gene regulation

Titelblatt und Inhaltsverzeichnis Einleitung Material und Methoden Ergebnisse Diskussion Zusammenfassung Literatur Abkuerzungen und AnhangDie Bindung extrazellulärer Liganden an Rezeptoren der Zelloberfläche kann binnen weniger Minuten das Genexpressionsprofil einer Zelle grundlegend ändern. Signalüberträger wie die Signaltransduktoren und Aktivatoren der Transkription (STAT)-Proteine, die die zelluläre Ant-wort auf zahlreiche Cytokine und Wachstumsfaktoren vermitteln, verbinden dabei die aktivierten Rezeptoren an der Zelloberfläche mit Transkriptionsereignissen im Kern. Wie die vorliegende Arbeit erstmals demonstriert, spielt die nucleo- cytoplasmatische Transportrate von Signalüber-trägern eine kritische Rolle bei der Modulation des vom Rezeptor ausgehenden Signals. So kon-trolliert der Export über die Verfügbarkeit am Rezeptor-Kinase-Komplex die Aktivierbarkeit von STAT-Transkriptionsfaktoren und reguliert damit die Spezifität und Signalstärke einer Cytokin-Antwort. Es konnte gezeigt werden, dass die Expression der alternativ gespleißten Transaktivie-rungsdomäne und ihre Signal-abhängige Serin727-Phosphorylierung den Export von STAT1 be- schleunigen. Mechanistisch scheint diese Regulation unabhängig von nukleären Retentionsfakto-ren und dem Exportrezeptor CRM1 zu sein. Die hier vorgestellten Ergebnisse enthüllen eine doppelte Funktion für die C-terminale Transaktivierungsdomäne: Zum einen reduziert die Ex-pression des C-Terminus die intranukleäre Mobilität von Tyrosin-phosphoryliertem STAT1. Dies erhöht die Retention im Kern und ist vermutlich auf die zu erwartende erhöhte Einbindung von aktiviertem STAT1 in Transkriptionskomplexen auf DNA zurückzuführen. Zum anderen er-leichtert dieselbe Domäne nach Tyrosin- Dephosphorylierung den Kernexport und fördert so die Rephosphorylierung im Cytoplasma. Aus diesem Grund unterscheiden sich die beiden Spleißva-rianten STAT1 und STAT1 bei gleicher Affinität zum Rezeptor-Kinase-Komplex stark in der Amplitude ihrer Tyrosin-Phosphorylierung und der Dauer des Signals. In Reportergen-Experimenten konnte gezeigt werden, dass der Export einen Anteil von etwa 20% an der nach Serin727-Phosphorylierung erhöhten Transaktivierungsaktivität von STAT1 hat. Ausgangspunkt dieser Arbeit war die Analyse N-terminal deletierter STAT1-Derivate, die ergab, dass der N-Terminus von STAT1 für die Bindung an den Importrezeptor Importin 5 und somit den Kern-import des Tyrosin-phosphorylierten Moleküls erforderlich ist. Dagegen wird der Kerntransport von unphosphoryliertem STAT1 von einer Deletion des N-Terminus nicht beeinflusst. Aus die-sem Grund unterbleibt nach Cytokin- Stimulation eine Kernakkumulation und der fortlaufende Export wird sichtbar. Diese Erkenntnis bildete die Grundlage für einen neuen Assay, mit dem der Export von STAT1 in Cytokin-stimulierten Zellen erstmals untersucht werden konnte. Die hier vorgestellten Ergebnisse fügen sich zu einem neuen Modell, dass die STAT-Aktivierung als ei-nen dynamischen Signalzyklus darstellt, der über das Zusammenspiel von konstitutiven, Signal-unabhängigen und induzierten, Signal-abhängigen Transportmechanismen die Intensität der Cy-tokin-induzierten Genexpression reguliert.Binding of extracellular ligands to cell-surface receptors can change the gene expression profile of a cell within minutes. Signal transmitters such as the signal transducer and activator of tran-scription (STAT) proteins, that mediate the cellular response to numerous cytokines and growth factors, link activated receptors at the cell membrane with transcriptional control in the nucleus. Here, we demonstrate for the first time that the rate of nucleo- cytoplasmic shuttling of signal transducers plays a critical role in modulating the signal that emanates from the receptor. Nuclear export controls the activation of STAT-transcription factors by regulating their availability at the receptor-kinase-complex. This determines the extent and specificity of the cytokine response. It was shown that expression of the alternatively spliced transactivation domain and its signal-dependent serine phosphorylation increase the rate of STAT1 nuclear export. Mechanistically, this regulation seems to be independent of nuclear retention factors and the export receptor CRM1. Our results disclose a dual function for the C-terminal transactivation domain; on the one hand, expression of the C-terminus reduces the intranuclear mobility of tyrosine-phosphorylated STAT1. Presumably this results from increased retention of activated STAT1 within transcrip-tional complexes on DNA. On the other hand, the same domain facilitates nuclear export after tyrosine dephosphorylation and thus promotes re-activation in the cytoplasm. Therefore, despite their identical receptor recognition, the two splice variants STAT1 und STAT1 differ strongly in the level of tyrosine phosphorylation and in the duration of the signal. Reportergene assays show, that facilitated nuclear export accounts for about 20% of the stimulatory influence of serine phosphorylation on STAT1 transcriptional activity. Starting point of this study was the charac-terisation of N-terminally truncated STAT1 mutants. Their analysis uncovered that the N-Domain of STAT1 is required for binding to the import receptor Importin 5 und thus nuclear import of tyrosine-phosphorylated STAT1. Nevertheless deletion of the N-domain did not affect the consti-tutive nucleo-cytoplasmic transport of the unphosphorylated protein. Hence, cytokine induced nuclear accumulation is prevented and the ongoing nuclear export is revealed. These findings provided the basis for a novel assay, that enabled the analysis of STAT1 nuclear export in cyto-kine stimulated cells. The results presented here comply with a new model that describes STAT activation as a dynamic signalling cycle. The combination of constitutive, signal-independent and induced, signal-dependent transport mechanisms control the intensity of cytokine induced gene expression