Structural analysis of B-Box 2 from MuRF1: identification of a novel self-association pattern in a RING-like fold

The B-box motif is the defining feature of the TRIM family of proteins, characterized by a RING finger-B-box-coiled coil tripartite fold. We have elucidated the crystal structure of B-box 2 (B2) from MuRF1, a TRIM protein that supports a wide variety of protein interactions in the sarcomere and regulates the trophic state of striated muscle tissue. MuRF1 B2 coordinates two zinc ions through a cross-brace alpha/beta-topology typical of members of the RING finger superfamily. However, it self-associates into dimers with high affinity. The dimerization pattern is mediated by the helical component of this fold and is unique among RING-like folds. This B2 reveals a long shallow groove that encircles the C-terminal metal binding site ZnII and appears as the defining protein-protein interaction feature of this domain. A cluster of conserved hydrophobic residues in this groove and, in particular, a highly conserved aromatic residue (Y133 in MuRF1 B2) is likely to be central to this role. We expect these findings to aid the future exploration of the cellular function and therapeutic potential of MuRF1.

Selective pharmacological targeting of a DEAD box RNA helicase

RNA helicases represent a large family of proteins implicated in many biological processes including ribosome biogenesis, splicing, translation and mRNA degradation. However, these proteins have little substrate specificity, making inhibition of selected helicases a challenging problem. The prototypical DEAD box RNA helicase, eIF4A, works in conjunction with other translation factors to prepare mRNA templates for ribosome recruitment during translation initiation. Herein, we provide insight into the selectivity of a small molecule inhibitor of eIF4A, hippuristanol. This coral-derived natural product binds to amino acids adjacent to, and overlapping with, two conserved motifs present in the carboxy-terminal domain of eIF4A. Mutagenesis of amino acids within this region allowed us to alter the hippuristanol-sensitivity of eIF4A and undertake structure/function studies. Our results provide an understanding into how selective targeting of RNA helicases for pharmacological intervention can be achieved.

Steady streaming in a two-dimensional box model of a passive cochlea

Acoustic stimulation of the cochlea leads to a travelling wave in the cochlear fluids and on the basilar membrane (BM). It has long been suspected that this travelling wave leads to a steady streaming flow in the cochlea. Theoretical investigations suggested that the steady streaming might be of physiological relevance. Here, we present a quantitative study of the steady streaming in a computational model of a passive cochlea. The structure of the streaming flow is illustrated and the sources of streaming are closely investigated. We describe a source of streaming which has not been considered in the cochlea by previous authors. This source is also related to a steady axial displacement of the BM which leads to a local stretching of this compliant structure. We present theoretical predictions for the streaming intensity which account for these new phenomena. It is shown that these predictions compare well with our numerical results and that there may be steady streaming velocities of the order of millimetres per second. Our results indicate that steady streaming should be more relevant to low-frequency hearing because the strength of the streaming flow rapidly decreases for higher frequencies.

Pralines from a smaller gift box taste better

This study shows that taste ratings of repeatedly chosen pralines decrease more when the gift box is large compared to small. Within their first choices consumers select the most preferred praline less often from the large assortment. These results are discussed in the light of variety seeking and dysfunctional choice.

Die Black Box der Studierenden: Studienmotivation und -verhalten vor und nach der Bologna-Reform

Die Universitäten in Deutschland und der Schweiz haben in den letzten zehn Jahren eine Reihe von Reformen und Veränderungen erlebt. Insbesondere die Bologna-Reform, aber auch die gestiegenen Studierendenzahlen werden dabei mit einer Reihe von nachteiligen Konsequenzen in Verbindung gebracht. In diesem Beitrag untersuchen wir die Frage, inwiefern sich die auf das Studium bezogenen Einstellungen und Verhaltensweisen der Studierenden nach der Bologna-Reform verändert haben. Unsere Datenbasis sind zwei umfangreiche Befragungen, die 2001 und 2012 an der Universität Bern durchgeführt wurden. Die Ergebnisse zeigen, dass sich die soziodemographische Zusammensetzung der Studierenden zwar deutlich verändert hat. Der zeitliche Aufwand für das Studium, die Leistungsmotivation der Studierenden, die Erwerbspartizipation oder der berichtete Zeitdruck haben aber in den letzten zehn Jahren wider Erwarten keine wesentlichen Veränderungen erfahren. Allerdings verfolgen heute mehr Studierende das Ziel, eine gute soziale Position und ein höheres Einkommen zu erreichen. Vor dem Hintergrund dieser Ergebnisse erscheint eine Reform der Reform nicht zwingend erforderlich zu sein.

Insulin, CCAAT/enhancer-binding proteins and lactate regulate the human 11β-hydroxysteroid dehydrogenase type 2 gene expression in colon cancer cell lines.

11β-Hydroxysteroid dehydrogenases (11beta-HSD) modulate mineralocorticoid receptor transactivation by glucocorticoids and regulate access to the glucocorticoid receptor. The isozyme 11beta-HSD2 is selectively expressed in mineralocorticoid target tissues and its activity is reduced in various disease states with abnormal sodium retention and hypertension, including the apparent mineralocorticoid excess. As 50% of patients with essential hypertension are insulin resistant and hyperinsulinemic, we hypothesized that insulin downregulates the 11beta-HSD2 activity. In the present study we show that insulin reduced the 11beta-HSD2 activity in cancer colon cell lines (HCT116, SW620 and HT-29) at the transcriptional level, in a time and dose dependent manner. The downregulation was reversible and required new protein synthesis. Pathway analysis using mRNA profiling revealed that insulin treatment modified the expression of the transcription factor family C/EBPs (CCAAT/enhancer-binding proteins) but also of glycolysis related enzymes. Western blot and real time PCR confirmed an upregulation of C/EBP beta isoforms (LAP and LIP) with a more pronounced increase in the inhibitory isoform LIP. EMSA and reporter gene assays demonstrated the role of C/EBP beta isoforms in HSD11B2 gene expression regulation. In addition, secretion of lactate, a byproduct of glycolysis, was shown to mediate insulin-dependent HSD11B2 downregulation. In summary, we demonstrate that insulin downregulates HSD11B2 through increased LIP expression and augmented lactate secretion. Such mechanisms are of interest and potential significance for sodium reabsorption in the colon.

Pandora's box and retrorectal tumors in laparoscopy: A case report and review of the literature.

INTRODUCTION Retrorectal tumors are uncommon and the etiology diverse. Literature to define the preoperative diagnosis and plan the intraoperative management are uncommon. PRESENTATION OF CASE We describe a case of a 44 year old patient with a laparoscopic approach for the removal of a retrorectal tumor and emphasize on the preoperative diagnostics and the intraoperative, minimal invasive approach. DISCUSSION Especially because these tumors are rare and often an incidental finding in gynecologic surgery, it is important to know the various differential diagnoses and its consequences with the laparoscopic approach. CONCLUSION We suggest the laparoscopic approach in cases of retroperitoneal cysts of unknown origin is ideal also because anatomic structures, mostly nerves, can be easily spared.