760 research outputs found
Regulation of Dpp target genes by Mad/Medea and Brinker
No full textThe TGF-β family member Decapentaplegic (Dpp) is a key regulator of patterning and
growth in development of Drosophila. Binding of Dpp to its receptors triggers the activation
of the intracellular Smad pathway. It has recently been shown that Dpp signalling represses
genes in several tissues by direct binding of the Smad proteins Mad and Medea and the
recruitment of the nuclear zinc finger protein Schnurri to small regulating sequences called
Silencer Elements (SEs). A key target of this SE-mediated repression is the brinker gene.
Brinker is the default repressor of the Dpp signalling pathway and its removal is a prerequisite
for transcriptional activation of most of the Dpp target genes.
To address the question if there is, analogous to the SE-mediated repression, also a simple,
not tissue-specific mechanism to activate target genes, we analyzed the regulation of dad. The
dad gene encodes the only Drosophila inhibitory Smad and is a potential direct target of Dpp
signalling. We identified the minimal enhancer of dad and discovered a short motif that we
called Activating Element (AE). The sequence of the AE is closely related to the one of the
SE, but differs in important nucleotides. As a consequence, the AE cannot recruit the
repressor Schnurri. We demonstrated that the AE integrates both repressive input by Brinker
as well as activating input by Mad and Medea. After characterization of the AE and
elaboration of a consensus sequence, we were able to predict and successfully identify
functional AEs in enhancers of other known (and hitherto unknown) direct target genes of
Dpp. This is the first description of an activating Dpp-response element that is not restricted
to a distinct enhancer and marks a general mechanism by which Dpp can activate target
genes
Folding of the transcription factor Brinker and interactions of the bacterial second messenger c-di-GMP studied by NMR
No full textNuclear magnetic resonance (NMR) spectroscopy is a technique, which allows the non-invasive investigation of
structures, dynamics and interactions of biomolecules.
The main goal of this thesis was to elucidate the folding mechanism of the transcription factor Brinker and its
implications for DNA recognition as well as the characterization of unfolded protein states by NMR.
This constitutes the first part of this thesis.
The transcription factor Brinker is a nuclear repressor, which is involved in
cellular growth and differentiation.
In the absence of DNA, Brinker is completely disordered.
However, in the presence of DNA or at low temperatures, the Brinker DNA binding domain (BrkDBD) adopts a well-folded structure.
Thus, BrkDBD represents an extreme case of the coupling between binding and folding phenomenon.
We have aimed to elucidate this folding mechanism in order to understand its implications for DNA recognition.
From our data, it is clear that the BrkDBD folding energy landscape sharply depends on buffer anion type and concentration.
We show that folded BrkDBD always adopts the same structure irrespective of the conditions.
Our data indicate helical propensity for 3 of the 4 native helices even in unfolded BrkDBD, which may serve as
initial contact points for DNA recognition.
Resonance broadening due to conformational exchange on the micro- to millisecond time scale between folded and
unfolded BrkDBD was analyzed by NMR relaxation dispersion experiments indicating a two-state
folding mechanism.
Only few residues show a different behavior and these are all located at the DNA binding interface.
This local conformational heterogeneity may be important for DNA recognition.
Based on these findings, we propose a mechanism of DNA recognition by BrkDBD, where the electrostatics-driven folding
is a key component, accelerating the recognition process.
In addition, we have analyzed the side-chain chi1-rotamer distribution of urea-denatured ubiquitin and protein G,
revealing that individual residues show significant deviations from statistical-coil ensemble averages,
indicating local bias towards the folded state.
The second part of this thesis describes the quantitative characterization of the intermolecular interactions between monomers
of the bacterial second messenger c-di-GMP at physiologically relevant concentrations.
C-di-GMP is a bacterial second messenger, involved in many signaling events.
Its most important effect is to trigger the transition from motile to sessile bacterial life-styles which plays a major
role in biofilm formation.
In solution, c-di-GMP has been reported to form several oligomers in the presence of monovalent cations, particularly
potassium.
However, only monomeric and dimeric c-di-GMP have been observed in complexes with proteins or RNA.
We have carried out a detailed kinetic and thermodynamic analysis of c-di-GMP polymorphism in the presence of potassium,
which showed that predominantly monomers and only few dimers exist at physiological concentrations.
Additionally, we present NOE and ROE structural information on c-di-GMP oligomers, which
indicate that these are not entirely all-syn and all-anti as opposed to the literature
Unraveling Mechanisms of Transcriptional Repression: Novel Insights from Brinker
No full textTranscriptional repressors bind cis-regulatory elements of target genes in a sequence specific manner. To antagonize transcription, repressors primarily function by recruiting accessory proteins, co-repressors, which in turn largely function by modifying chromatin structure. Although a repressor could function by recruiting just a single co-repressor, many recruit more than one, with Brinker (Brk) from Drosophila recruiting the co-repressors, CtBP and Groucho (Gro), in addition to possessing a third repression domain, 3R. Previous studies indicated that Gro is sufficient for Brk to repress target genes in the wing imaginal disc, questioning why it should need to recruit CtBP, a ’short-range’ co-repressor compared to Gro that can function over longer distances. To resolve this I have used genomic engineering to generate a series of endogenous brk mutants that are unable to recruit Gro, CtBP and/or have the 3R domain deleted. Analysis of these mutants reveals that while the recruitment of Gro is necessary and is almost sufficient for Brk to make a morphologically wild-type fly, it is insufficient during oogenesis where Brk must utilize CtBP and 3R to pattern the egg-shell appropriately. Gro insufficiency during oogenesis can be explained by its downregulation in Brk-expressing cells through phosphorylation downstream of EGFR signaling, thus making it unavailable for Brk which must then resort to CtBP and/or 3R for repressive activity. The present study dissects the mechanism of activity of a transcription factor and its co-repressors and is the first to do so in multicellular eukaryotes in a physiologically relevant manner; additionally its findings provide a better understanding of why transcription factors in general may utilize more than one co-repressor
Characterization of Schnurri : an integral component of the Dpp-signaling pathway in "Drosophila melanogaster"
No full textSignaling by the transforming growth factor-β (TGF-β) family of ligands plays a crucial role during development and tissue homeostasis in all multicellular organisms. The signal transduction pathway is highly conserved and relatively simple. Ligand mediated receptor activation induces heteromerization and nuclear translocation of the signal mediators, the Smad proteins. Once in the nucleus, the Smad complexes bind to and regulate directly a large number of target genes. Intriguingly, only a few Smad proteins mediate the majority of the complex cellular responses elicited by ligands of the TGF-β family by either transcriptional activation or repression, depending on their associated partners. A number of Smad interacting proteins and modulators have been identified, partly explaining the diversity of transcriptional outcome. Nevertheless, the biological consequences and their role in developmental aspects of TGF-β signaling are poorly understood. The best characterized member of the TGF-β family in Drosophila melanogaster is Decapentaplegic (Dpp). Dpp plays important roles during development and its cellular function has been extensively investigated in genetic experiments. One of the main Dpp-target genes during development encodes a repressor protein, Brinker. Brinker suppresses the transcription of Dpp-target genes and is itself negatively regulated by Dpp-signaling. This down-regulation of brinker by Dpp is essential for Dpp target genes to become activated. The molecular basis of the Dpp-mediated repression is elusive; however, genetic studies identified the gene schnurri (shn) to be required for this activity. In this thesis, the results of a detailed structure-function analysis of the nuclear zinc finger protein Schnurri are presented. It could be demonstrated that Schnurri protein, together with the Drosophila Smads Mad and Medea, forms a signal-dependant DNA-protein complex on short silencer elements within the brinker regulatory region. The recruitment of Schnurri to the silencer elements by Mad/Medea is required for the transcriptional regulatory activity of the complex in vivo. Two modules within the Schnurri protein were identified that are required and sufficient for Dpp-mediated brinker repression in vivo. The two entities, a protein-DNA complex formation domain and a domain containing repressor activity, can be separated from each while retaining their function. The Schnurri protein presents the first interaction partner for Mad and Medea in Drosophila. Furthermore, Schnurri is the first examples that link TGF-β signaling to tissue-unspecific repression rather than activation
Rachel M. McCord, (1882-1965), purchased by Mrs. Thelma E. Brinker on April 10, 1965.
No full textDocuments regarding the double headstone for Rachel M. McCord, (1882-1965), buried with James L. McCord, (1876-1914), purchased by Mrs. Thelma E. Brinker. The marker was placed at Springfield Cemetery in Holland, Ohio. The stone is made of F/C/Black with Polish Bevel top in Sandblast letters. Rubbings is included
Man kann nicht nicht lernen! Informelle Lernprozesse von Studierenden der Hochschule Ostwestfalen‐Lippe in der Studieneingangsphase – dargestellt am Beispiel der Studienpioniere
No full textMertens C, Menz F, Vörtler S. Man kann nicht nicht lernen! Informelle Lernprozesse von Studierenden der Hochschule Ostwestfalen‐Lippe in der Studieneingangsphase – dargestellt am Beispiel der Studienpioniere. In: Brinker T, Gesellschaft für Schlüsselkomeptenzen in Lehre, Forschung und Praxis e.V., eds. Schlüsselkompetenzerwerb im Lernraum Studieneingangsphase und Studierfähigkeit. Westfälische Hochschule – 30.8.-1.9.2016 . 2017: 88-96
Interaktionsforschung/Sozialpsychologie und ihre Bedeutung für die Gesprächsanalyse.
No full textPaul I. Interaktionsforschung/Sozialpsychologie und ihre Bedeutung für die Gesprächsanalyse. In: Antos G, Brinker K, Heinemann W, Sager SF, eds. Text- und Gesprächslinguistik. Ein internationales Handbuch zeitgenössischer Forschung. Berlin/New York: De Gruyter; 2001: 903-908
Conventions, rules and maxims in conversation
No full textKindt W. Konventionen, Regeln und Maximen in Gesprächen. In: Brinker K, Antos G, Heinemann W, Sager SF, eds. Text- und Gesprächslinguistik: ein internatonales Handbuch zeitgenössischer Forschung. Halbbd. 2. Handbücher zur Sprach- und Kommunikationswissenschaft. Vol 16. Berlin: de Gruyter; 2001: 1178-1187
Projektarbeit durch Studierendengruppen als interdisziplinäre Pflichtveranstaltung
No full textMertens C, Doleschal R, Villmer FJ. Projektarbeit durch Studierendengruppen als interdisziplinäre Pflichtveranstaltung. In: Brinker T, Rössler U, eds. Hochschuldidaktik an Fachhochschulen Neue Ansätze in der Lehre aus den Fachhochschulen des Landes Nordrhein‐Westfalen . Blickpunkt Hochschuldidaktik. Vol 113. Bielefeld: Bertelsmann ; 2004: 47-56
Final Report Levee Challenge: Team Hans Brinker
No full textIn this assignment we simulate a two meters wide dike stretch which is subjected to overflow. Three failure mechanisms could occur due to overflow: full erosion of the soil of the dike, macro instability of the levee if too much soil is eroded away, leading to insufficient counterweight on the inside of the levee, and surface slip failure due to reduction of strength of the dike by flow of water in the dike core. Prevention of failure can be achieved by either keeping the water away from the berm surface or holding the soil particles in place while the water flows alongside it. The desired repair is an emergency repair that can placed quickly during a storm, or between two storms to prevent a damaged levee from failing. This is a temporary repair that will later be removed for full reconstruction of the levee. This provides constraints to the installation and repair procedure.To decide which solution is best, 10 concept solutions are compared based on their score in the Multi Criteria Analysis with 8 weighted criteria. The solution with the highest score is the best solution according to the Multi Criteria Analysis. The selected repair option is to locally cover the damaged area with flexible overlapping sheets of Tyvek®. This is a light and thin material that can easily be transported and cut to size at the location of the repair. These sheets can be easily secured against flow loads using Gripple anchors, while pins are used to keep the Tyvek® in place during windy conditions. An installation plan and cost breakdown was made. Using 3 m wide Tyvek® rolls, the costs would be around 19.19 euros per meter height.The damaged areas of the levee are covered with Tyvek® which is a waterproof, damp open material. This prevents the penetration of water into the core through the damaged areas. The Tyvek® also prevents the exposed soil from being eroded. Moreover, Tyvek® is a very strong material that won’t be torn off. As there is no strength reduction due to water penetration or further loss of surface material the chance for macro instability is minimized.First, a design was created, with components dimensioned for a dike stretch in the Hedwigepolder. Subsequently, the design was validated with tests. Including two types of damage. The first was removal of a 2 by 2 m grass layer (0.1 m thick) at the top of the dike and the second was a dug-out step-section across the entire width of the dike with a height difference of 0.5 meters at the toe of the dike. Only the second damage went through the clay layer and into the sand core of dike.During and after the tests some important observations were made. During all test volumes the plastic sheets were kept in place due to the anchors and pins. Some pins however, came loose due to vibration of the sheets (we presumed the cause of vibration is flow of water between two sheets or turbulence of water). The trench of the lower damage was partly washed away by the water. The erosion of soil in the trench did not result in changing the stability of the top sheet. At the lower damage the plastic sheet was torn off after a tear of 1 m was made with a knife.Our solution is designed to protect any dike from macro-instability by keeping the water flow away from the berm. This is done by layering multiple sheets of plastic foil over the inner berm, fastened with ground anchors and pins. The solution is a durable and reliable design due to proven waterproof, damp open and UV resistant properties, together with Gripple's demonstrated anchoring capabilities. Another major advantage of our solution is that the repair of the damage is selective, i.e. the solution is applied only to the parts of the levee where damage has occurred. In case of only localized and small damage to the levee, the costs and workload are very minimal compared to other solutions that are applied to the entire surface area of the levee.Polder2CCivil Engineerin
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