Signaling pathway of a photoactivable Rac1-GTPase in the early stages

In modern life- and medical-sciences major efforts are currently concentrated on creating artificial photoenzymes, consisting of light- oxygen-voltage-sensitive (LOV) domains fused to a target enzyme. Such protein constructs possess great potential for controlling the cell metabolism as well as gene function upon light stimulus. This has recently been impressively demonstrated by designing a novel artificial fusion protein, connecting the AsLOV2-Jα-photosensor from Avena sativa with the Rac1-GTPase (AsLOV2-Jα-Rac1), and by using it, to control the motility of cancer cells from the HeLa-line. Although tremendous progress has been achieved on the generation of such protein constructs, a detailed understanding of their signaling pathway after photoexcitation is still in its infancy. Here, we show through computer simulations of the AsLOV2-Jα-Rac1-photoenzyme that the early processes after formation of the Cys450-FMN-adduct involve the breakage of a H-bond between the carbonyl oxygen FMN-C4O and the amino group of Gln513, followed by a rotational reorientation of its sidechain. This initial event is followed by successive events including β-sheet tightening and transmission of torsional stress along the Iβ-sheet, which leads to the disruption of the Jα-helix from the N-terminal end. Finally, this process triggers the detachment of the AsLOV2-Jα-photosensor from the Rac1-GTPase, ultimately enabling the activation of Rac1 via binding of the effector protein PAK1.

CopY-like copper inducible repressors are putative 'winged helix' proteins

CopY of Enterococcus hirae is a well characterized copper-responsive repressor involved in copper homeostasis. In the absence of copper, it binds to the promoter. In high copper, the CopZ copper chaperone donates copper to CopY, thereby releasing it from the promoter and allowing transcription of the downstream copper homeostatic genes of the cop operon. We here show that the CopY-like repressors from E. hirae, Lactococcus lactis, and Streptococcus mutans have similar affinities not only for their native promoters, but also for heterologous cop promoters. CopZ of L. lactis accelerated the release of CopY from the promoter, suggesting that CopZ of L. lactis acts as copper chaperone, similar to CopZ in E. hirae. The consensus binding motif of the CopY-like repressors was shown to be TACAxxTGTA. The same binding motif is present in promoters controlled by BlaI of Bacillus licheniformis, MecI of Staphylococcus aureus and related repressors. BlaI and MecI have known structures and belong to the family of 'winged helix' proteins. In the N- terminal domain, they share significant sequence similarity with CopY of E. hirae. Moreover, they bind to the same TACAxxTGTA motif. NMR analysis of the N-terminal DNA binding domain of CopY of L. lactis showed that it contained the same alpha-helical content like the same regions of BlaI and MecI. These findings suggest that the DNA binding domains of CopY-like repressors are also of the 'winged helix' type.

The Role of Corruption in Explaining the Electoral Success of New Political Parties in Central and Eastern Europe

More than 20 years after the collapse of the Soviet Union, the electoral volatility in Central and Eastern Europe (CEE) is still remarkably high. A considerable part of the volatility derives from the votes for new political parties, since they are very often on the winning side of elections. This paper examines corruption as potential determinant of their electoral success. It argues that the effect of corruption is twofold: On the onehand, the historically-grown corruption level reduces the electoral success of new political parties due to strong clientelist structures that bind the electorate to the established parties. On the other hand, an increase of the perceived corruption above the traditional corruption level leads to a loss of trust in the political elite and therefore boosts the electoral success of new competitors. A statistical analysis of all democratic elections in CEE between 1996 and 2011 confirms these two counteracting effects.

What is the Role of Universities in High-tech Economic Development? The Case of Portland, Oregon, and Washington, DC

This paper focuses on two regions in the United States that have emerged as high-technology regions in the absence of major research universities. The case of Portland's Silicon Forest is compared to Washington, DC. In both regions, high-technology economies grew because of industrial restructuring processes. The paper argues that in both regions other actors—such as firms and government laboratories—spurred the development of knowledge-based economies and catalysed the engagement of higher education institutions in economic development. The paper confirms and advances the triple helix model of university–government–industry relationships and posits that future studies have to examine degrees of university-region engagement.

Corruption and the Electoral Support of New Political Parties in Central and Eastern Europe

More than 20 years after the collapse of the Soviet Union, the electoral volatility in Central and Eastern Europe (CEE) is still remarkably high. A considerable part of the volatility derives from the votes for new political parties, since they are very often on the winning side of elections. This article examines corruption as a potential determinant of their electoral support. It argues that the effect of corruption is twofold: on the one hand, the historically derived corruption level reduces the electoral support for new political parties due to strong clientelist structures that bind the electorate to the established parties. On the other hand, an increase in perceived corruption above the traditional corruption level leads to a loss of trust in the political elite and therefore boosts the electoral support for new competitors. A statistical analysis of all democratic elections in CEE between 1996 and 2013 confirms these two counteracting effects.

Convergent synthesis and cellular uptake of multivalent cell penetrating peptides derived from Tat, Antp, pVEC, TP10 and SAP

Cell penetrating peptides (CPP) are peptides of 10 to 30 residues derived from natural translocating proteins. Multivalency is known to enhance cellular uptake for the Tat peptide and closely related polycationic sequences. To test whether multivalency effects on cellular uptake might also occur with other CPP types, we prepared multivalent versions of the strongly cationic Tat, the amphipathic sequences Antp, pVEC and TP10, and the polyproline helix SAP by convergent thioether ligation of the linear CPP onto multivalent scaffolds, and evaluated their uptake in HeLa and CHO cells, intracellular localization, cytotoxicity and hemolysis. While multivalency did not increase the cellular uptake of pVEC or SAP, multivalency effects on uptake comparable to Tat were observed with TP10 and Antp, which are attributable to their polycationic nature. The efficient synthetic protocol for these divalent CPP and their localization in the cytoplasm suggest that CPP might be useful for application in cargo delivery into cells.

Tandem Mass Spectrometric Analysis of Metallocene Adducts with Short Oligonucleotides

Metallocene dichlorides constitute a remarkable class of antineoplastic agents that are highly effective against several cancer cell lines. They were shown to accumulate in the DNA-rich region, which suggests DNA as the primary target. These compounds exhibit two cyclopentadienyl ligands and two labile halide ligands, resulting in a bent sandwich structure. The cis-dihalide motif is structurally related to the cis-chloro configuration of cisplatin and similar modes of action can thus be assumed. Cisplatin binds to two neighboring guanine nucleobases in DNA and consequently, distorts the double-helix, thereby inhibiting DNA replication and transcription. Platinum is classified as a soft Lewis acid and binds preferentially to the nitrogen atoms within the nucleobases. The metallocene dichlorides investigated in this study comprise the metal centers Ti, V, Nb, Mo, Hf, and W, which are classified as hard or intermediate Lewis acids, and thus, favor binding to the phosphate oxygen. Although several studies reported adduct formation of metallocene dichlorides with nucleic acids, substantial information about the adduct composition, the binding pattern, and the nucleobase selectivity has not been provided yet. ESI-MS analyses gave evidence for the formation of metallocene adducts (M = Ti, V, Mo, and W) with single-stranded DNA homologues at pH 7. No adducts were formed with Nb and Hf at neutral pH, albeit adducts with Nb were observed at a low pH. MS2 data revealed considerable differences of the adduct compositions. The product ion spectra of DNA adducts with hard Lewis acids (Ti, V) gave evidence for the loss of metallocene ligands and only moderate backbone fragmentation was observed. By contrast, adducts with intermediate Lewis acids (Mo, W) retained the hydroxy ligands. Preliminary results are in good agreement with the Pearson concept and DFT calculations. Since the metallodrugs were not lost upon CID, the nucleobase selectivity, stoichiometry, and binding patterns can be elucidated by means of tandem mass spectrometry.

X-ray structure of a lectin-bound DNA duplex containing an unnatural phenanthrenyl pair

DNA duplexes containing unnatural base-pair surrogates are attractive biomolecular nanomaterials with potentially beneficial photophysical or electronic properties. Herein we report the first X-ray structure of a duplex containing a phen-pair in the center of the double helix in a zipper like stacking arrangement.

The Ras inhibitors caveolin-1 and docking protein 1 activate peroxisome proliferator-activated receptor ? through spatial relocalization at helix 7 of its ligand-binding domain

Peroxisome proliferator-activated receptor ? (PPAR?) is a transcription factor that promotes differentiation and cell survival in the stomach. PPAR? upregulates and interacts with caveolin-1 (Cav1), a scaffold protein of Ras/mitogen-activated protein kinases (MAPKs). The cytoplasmic-to-nuclear localization of PPAR? is altered in gastric cancer (GC) patients, suggesting a so-far-unknown role for Cav1 in spatial regulation of PPAR? signaling. We show here that loss of Cav1 accelerated proliferation of normal stomach and GC cells in vitro and in vivo. Downregulation of Cav1 increased Ras/MAPK-dependent phosphorylation of serine 84 in PPAR? and enhanced nuclear translocation and ligand-independent transcription of PPAR? target genes. In contrast, Cav1 overexpression sequestered PPAR? in the cytosol through interaction of the Cav1 scaffolding domain (CSD) with a conserved hydrophobic motif in helix 7 of PPAR?'s ligand-binding domain. Cav1 cooperated with the endogenous Ras/MAPK inhibitor docking protein 1 (Dok1) to promote the ligand-dependent transcriptional activity of PPAR? and to inhibit cell proliferation. Ligand-activated PPAR? also reduced tumor growth and upregulated the Ras/MAPK inhibitors Cav1 and Dok1 in a murine model of GC. These results suggest a novel mechanism of PPAR? regulation by which Ras/MAPK inhibitors act as scaffold proteins that sequester and sensitize PPAR? to ligands, limiting proliferation of gastric epithelial cells.

What sets the odds of winning and losing?

Social experience influences the outcome of conflicts such that winners are more likely to win again and losers will more likely lose again, even against different opponents. Although winner and loser effects prevail throughout the animal kingdom and crucially influence social structures, the ultimate and proximate causes for their existence remain unknown. We propose here that two hypotheses are particularly important among the potential adaptive explanations: the 'social-cue hypothesis', which assumes that victory and defeat leave traces that affect the decisions of subsequent opponents; and the 'self-assessment hypothesis', which assumes that winners and losers gain information about their own relative fighting ability in the population. We discuss potential methodologies for experimental tests of the adaptive nature of winner and loser effects.

The use of intramedullary helix wire for the treatment of proximal humerus fractures

OBJECTIVE: To present the functional and radiographic outcome 1 and 6 years after application of a new intramedullary fixation device for proximal humerus fractures. DESIGN: Retrospective case series. SETTING: Level II orthopaedic surgery hospital. PATIENTS: Twenty-six consecutive patients (average age 68.9 years) with 2-, 3- and 4-part fractures of the proximal humerus were operated at a single institution. Follow-up was performed after 1 year (26 patients) and 6 years (16 patients). INTERVENTION: All patients were treated with closed reduction and intramedullary helix wires. MAIN OUTCOME MEASUREMENTS: The Constant-Murley score and the University of California Los Angeles (UCLA) score. Clinical complications and radiological posttraumatic arthritis were recorded. RESULTS: The average Constant-Murley score was 70.3 (points) and 70.7 after 1 and 6 years, respectively; the average UCLA score was 27.2 and 31.5 after 1 and 6 years, respectively. Major complications were 4 revisions for 3 secondary fragment displacements and 1 nonunion with partial avascular osteonecrosis in the first postoperative year. Complications were found predominantly in 4-part fractures (3/5, 60%). There were no further complications or progressive posttraumatic arthritis up to 6 years following surgery. CONCLUSION: The helix wire is well suited for displaced or unstable 2- and 3-part proximal humerus fractures. Adequate functional outcome, a low number of implant displacements, a low number of application morbidity, and infrequent implant removals were recorded. The use of this device is not recommended for 4-part fractures.

The copper-responsive repressor CopR of Lactococcus lactis is a 'winged helix' protein

CopR of Lactococcus lactis is a copper-responsive repressor involved in copper homoeostasis. It controls the expression of a total of 11 genes, the CopR regulon, in a copper-dependent manner. In the absence of copper, CopR binds to the promoters of the CopR regulon. Copper releases CopR from the promoters, allowing transcription of the downstream genes to proceed. CopR binds through its N-terminal domain to a 'cop box' of consensus TACANNTGTA, which is conserved in Firmicutes. We have solved the NMR solution structure of the N-terminal DNA-binding domain of CopR. The protein fold has a winged helix structure resembling that of the BlaI repressor which regulates antibiotic resistance in Bacillus licheniformis. CopR differs from other copper-responsive repressors, and the present structure represents a novel family of copper regulators, which we propose to call the CopY family.

Assembling Multiporphyrin Stacks Inside the DNA Double Helix

Double stranded DNA hybrids containing up to four consecutive, face-to-face stacked porphyrins are described. Non-nucleosidic, 5,15-bisphenyl-substituted porphyrin building blocks were incorporated into complementary oligonucleotide strands. Upon hybridization multiple porphyrins are well accommodated inside the DNA scaffold without disturbing the overall B-DNA structure. The formation of double strands containing up to four free base porphyrins is enabled without compromising duplex stability. UV/vis, fluorescence, and CD spectroscopy demonstrate the formation of porphyrins H-aggregates inside the DNA double helix and provide evidence for the existence of strong excitonic coupling between interstrand stacked porphyrins. H-aggregation results in considerable fluorescence quenching. Most intense CD effects are observed in stacks containing four porphyrins. The findings demonstrate the value of DNA for the controlled formation of molecularly defined porphyrin aggregates.

Triple-helix formation in the antiparallel binding motif of oligodeoxynucleotides containing N(9)- and N(7)-2-aminopurine deoxynucleosides

Triplex-forming oligodeoxynucleotide 15mers, designed to bind in the antiparallel triple-helical binding motif, containing single substitutions (Z) of the four isomeric alphaN(7)-, betaN(7)-, alphaN(9)- and betaN(9)-2-aminopurine (ap)-deoxyribonucleosides were prepared. Their association with double-stranded DNA targets containing all four natural base pairs (X-Y) opposite the aminopurine residues was determined by quantitative DNase I footprint titration in the absence of monovalent metal cations. The corresponding association constants were found to be in a rather narrow range between 1.0 x 10(6) and 1.3 x 10(8) M(-1). The following relative order in Z x X-Y base-triple stabilities was found: Z = alphaN(7)ap: T-A > A-T> C-G approximately G-C; Z = betaN(7)ap: A-T > C-G > G-C > T-A; Z = alphaN(9)ap: A-T = G-C > T-A > C-G; and Z = betaN(9)ap: G-C > A-T > C-G > T-A