A Novel Quality Control Compartment Derived from the Endoplasmic Reticulum

Degradation of proteins that, because of improper or suboptimal processing, are retained in the endoplasmic reticulum (ER) involves retrotranslocation to reach the cytosolic ubiquitin-proteasome machinery. We found that substrates of this pathway, the precursor of human asialoglycoprotein receptor H2a and free heavy chains of murine class I major histocompatibility complex (MHC), accumulate in a novel preGolgi compartment that is adjacent to but not overlapping with the centrosome, the Golgi complex, and the ER-to-Golgi intermediate compartment (ERGIC). On its way to degradation, H2a associated increasingly after synthesis with the ER translocon Sec61. Nevertheless, it remained in the secretory pathway upon proteasomal inhibition, suggesting that its retrotranslocation must be tightly coupled to the degradation process. In the presence of proteasomal inhibitors, the ER chaperones calreticulin and calnexin, but not BiP, PDI, or glycoprotein glucosyltransferase, concentrate in the subcellular region of the novel compartment. The “quality control” compartment is possibly a subcompartment of the ER. It depends on microtubules but is insensitive to brefeldin A. We discuss the possibility that it is also the site for concentration and retrotranslocation of proteins that, like the mutant cystic fibrosis transmembrane conductance regulator, are transported to the cytosol, where they form large aggregates, the “aggresomes.”

Chromosomal localization of the proteasome Z subunit gene reveals an ancient chromosomal duplication involving the major histocompatibility complex.

Proteasomes are the multi-subunit protease thought to play a key role in the generation of peptides presented by major histocompatibility complex (MHC) class I molecules. When cells are stimulated with interferon gamma, two MHC-encoded subunits, low molecular mass polypeptide (LMP) 2 and LMP7, and the MECL1 subunit encoded outside the MHC are incorporated into the proteasomal complex, presumably by displacing the housekeeping subunits designated Y, X, and Z, respectively. These changes in the subunit composition appear to facilitate class I-mediated antigen presentation, presumably by altering the cleavage specificities of the proteasome. Here we show that the mouse gene encoding the Z subunit (Psmb7) maps to the paracentromeric region of chromosome 2. Inspection of the mouse loci adjacent to the Psmb7 locus provides evidence that the paracentromeric region of chromosome 2 and the MHC region on chromosome 17 most likely arose as a result of a duplication that took place at an early stage of vertebrate evolution. The traces of this duplication are also evident in the homologous human chromosome regions (6p21.3 and 9q33-q34). These observations have implications in understanding the genomic organization of the present-day MHC and offer insights into the origin of the MHC.

Mammalian Sug1 and c-Fos in the nuclear 26S proteasome.

In a search for regulatory proteins that interact with the leucine zipper motif of c-Fos in the yeast two-hybrid screen, we have identified a protein (FZA-B) that has extensive sequence similarity to SUG1 of Saccharomyces cerevisiae. Here we show that FZA-B can functionally substitute for SUG1 in yeast and that FZA-B interacts with Fos proteins in vitro through their leucine zippers. In rat liver and in HeLa cells, FZA-B is present in the 26S proteasome complex, as is c-Fos. Immobilized antibody raised against an FZA-B-specific peptide depleted peptidase activity, proteasomal proteins, FZA-B, and c-Fos from a 26S proteasome preparation. FZA-B is found predominantly in the nuclear fraction of COS cells expressing an FZA-B transgene and in the nuclear 26S proteasome of HeLa cells. We conclude that FZA-B is the mammalian homolog of SUG1 (mSug1) and that it is present in the nuclear 26S proteasome of cells. Our results suggest that mSug1 may be involved in the degradation of c-Fos and other transcription factors.

The proteolytic fragments generated by vertebrate proteasomes: structural relationships to major histocompatibility complex class I binding peptides.

Proteasomes are involved in the proteolytic generation of major histocompatibility complex (MHC) class I epitopes but their exact role has not been elucidated. We used highly purified murine 20S proteasomes for digestion of synthetic 22-mer and 41/44-mer ovalbumin partial sequences encompassing either an immunodominant or a marginally immunogenic epitope. At various times, digests were analyzed by pool sequencing and by semiquantitative electrospray ionization mass spectrometry. Most dual cleavage fragments derived from 22-mer peptides were 7-10 amino acids long, with octa- and nonamers predominating. Digestion of 41/44-mer peptides initially revealed major cleavage sites spaced by two size ranges, 8 or 9 amino acids and 14 or 15 amino acids, followed by further degradation of the latter as well as of larger single cleavage fragments. The final size distribution was slightly broader than that of fragments derived from 22-mer peptides. The majority of peptide bonds were cleaved, albeit with vastly different efficiencies. This resulted in multiple overlapping proteolytic fragments including a limited number of abundant peptides. The immunodominant epitope was generated abundantly whereas only small amounts of the marginally immunogenic epitope were detected. The frequency distributions of amino acids flanking proteasomal cleavage sites are correlated to that reported for corresponding positions of MHC class I binding peptides. The results suggest that proteasomal degradation products may include fragments with structural properties similar to MHC class I binding peptides. Proteasomes may thus be involved in the final stages of proteolytic epitope generation, often without the need for downstream proteolytic events.

Becoming a State: Zionist and Palestinian Movements for National Liberation

This study examines the road to statehood for the Zionist and Palestinian movements. There are three components which frame this investigation: 1. social movements and the practices in which they engage that are aimed at establishing statehood for a people; 2. distinctive configurations of the international system and the manner in which both the material and ideational foundations of that system pulls units towards conformity and predictable behavior; and finally, 3. the role of agency, that is, the way in which instrumentally rational individuals attempt to push the structure in which they are embedded towards a configuration that is better suited to their interests and objectives The most influential factor guiding these struggles for national liberation are those forces which emanate from the prevailing structure of the international system. Not only was it demonstrated that the established material and ideational preferences of existing states have strong bearing on a movement’s ideological orientation and by consequence its chosen course of struggle, but hegemonic order configurations also define political cleavages and in so doing present movement leaders with both tactical and strategic opportunities by harnessing or exploiting those cleavages. From the agency perspective, the cases showed that the leadership of each movement was highly influential in the determination of a movement’s success or failure.

Biochemical and functional characterization of the tumor suppressors BRCA1 and BAP1

L’ubiquitination est une modification post-traductionnelle qui joue un rôle majeur dans la régulation d’une multitude de processus cellulaires. Dans cette thèse, je discuterai de la caractérisation de deux protéines, BRCA1 et BAP1, soit deux suppresseurs de tumeurs fonctionnellement reliés. BRCA1, une ubiquitine ligase qui catalyse la liaison de l’ubiquitine à une protéine cible, est mutée dans les cancers du sein et de l'ovaire. Il est bien établi que cette protéine aide à maintenir la stabilité génomique suite à un bris double brin de l’ADN (BDB), et ce, à l’aide d’un mécanisme de réparation bien caractérisé appelé recombinaison homologue. Cependant, les mécanismes de régulation de BRCA1 suite à des stresses génotoxiques n’impliquant pas directement un BDB ne sont pas pleinement élucidés. Nous avons démontré que BRCA1 est régulée par dégradation protéasomale suite à une exposition des cellules à deux agents génotoxiques reconnus pour ne pas directement générer des BDBs, soit les rayons UV, qui provoquent la distorsion de l’hélice d’ADN, et le méthyle méthanesulfonate (MMS), qui entraîne l’alkylation de l’ADN. La dégradation de BRCA1 est réversible et indépendante des kinases associées à la voie des PI3 kinase, soit ATM, ATR et DNA-PK, protéines qui sont rapidement activées par les dommages à l’ADN. Nous proposons que la dégradation de BRCA1 prévienne son recrutement intempestif, ainsi que celui des facteurs qui lui sont associés, à des sites de dommages d’ADN qui ne sont pas des BDBs, et que cette régulation coordonne la réparation de l’ADN. L’enzyme de déubiquitination BAP1 a initialement été identifiée comme une protéine capable d’interagir avec BRCA1 et de réguler sa fonction. Elle est également connue pour sa capacité à se lier avec les protéines du groupe Polycomb, ASXL1 et ASXL2. Cependant, l’importance de ces interactions n’a toujours pas été établie. Nous avons démontré que BAP1 forme deux complexes protéiques mutuellement exclusifs avec ASXL1 et ASXL2. Ces interactions sont critiques pour la liaison de BAP1 à l’ubiquitine ainsi que pour la stimulation de son activité enzymatique envers l’histone H2A. Nous avons également identifié des mutations de BAP1 dérivées de cancers qui empêchent à la fois son interaction avec ASXL1 et AXSL2, et son activité de déubiquitinase, ce qui fournit un lien mécanistique direct entre la déubiquitination de H2A et la tumorigenèse. Élucider les mécanismes de régulation de BRCA1 et BAP1 menera à une meilleure compréhension de leurs rôles de suppresseurs de tumeurs, permettant ainsi d’établir de nouvelles stratégies de diagnostic et traitement du cancer.

"Viewers should not try this at home". Die Verfassungsgerichte Bosnien-Herzegowinas und Kosovos in deren Rolle als Schlichtungsinstanzen in ethnopolitischen Konflikten = The constitutional courts of Bosnia-Herzegovina and Kosovo in their role as arbitration bodies in ethno-political conflicts. EDAP 01/2014

The article analyzes the role of constitutional courts in Bosnia and Kosovo, both characterized by their partly internationalized membership, in the adjudication of cases that are highly controversial between the different ethno-political factions. The main focus is on the Constitutional Court of Bosnia, which presents one of the richest and most interesting examples of “lawfare” in divided societies. The concept of lawfare has been adapted to refer to the continuation of political battles by ethno-political actors through legal means, in this case, constitutional adjudication. In Kosovo, the Constitutional Court has been an important defender of diversity, albeit its primary focus and merit are to have contributed to the establishment of a concept of democracy close to the people of Kosovo. The article concludes that constitutional courts represent important institutions of internal conflict resolution in divided societies, which have been instrumental in shaping multiculturalism in these post-conflict societies divided by deep ethnic cleavages.

MODEL COUNTRIES IN POLITICAL ANALYSIS. Is Turkey a Model for State-Building in the Arab World? Jean Monnet Occasional Paper No. 10/2014

This study analyzes the Turkish case as a model country for the state-building processes in the Arab world in the aftermath of the Arab revolts that took place in Tunisia, Egypt and Libya. To this end, it deals with the Turkish case in three phases: the founding of the Turkish Republic, political developments until 2002, and the post-2002 Justice and Development Party period. The study focuses on state-society relations manifested in the form of a secular-religious cleavage intertwined with problematic civil-military relations. Each phase of Turkey’s history is compared to cleavages and civil-military relations in Egypt, Tunisia and Libya. After analyzing the constitution-making processes in the latter three countries following the Arab revolts, the study concludes by discussing the viability of the Turkish model in the light of Turkey’s search for a new constitution.

Transatlantic MRAs: Lessons for TTIP? CEPS Special Report No. 101/March 2015

It is striking that there is little or no mention in the TTIP debate so far of the US-EU Mutual Recognition Agreement (MRA) concluded in 1998. At the time, expectations of the gains from the MRA were high. One should expect the MRA to be instructive for TTIP and entail some lessons to be learned for today’s attempt to lower technical barriers to trade (TBTs) across the North Atlantic. We offer an analysis of the 1998 MRA, the difficulties in the prior negotiations and those during the implementation phase, the subsequent and present status of sectoral approaches. The MRA experience revealed clearly how difficult it is to accomplish the acceptance of all relevant aspects of conformity assessment of the trading partner for the mere purpose of testing and certifying export goods on the requirements of the importing economy. The MRA has succeeded only in a few sectors. However, the ambition in TTIP with respect to TBTs is said to go so much further. It is therefore important for all those involved or interested in TTIP to learn the lessons of this early exercise in lowering TBT costs. This paper reaches two main conclusions: i) the US-EU MRA was only partially successful and only for some one-fifth of the export flows at the time: a disappointing outcome and a far cry from the expectations of business and political leaders; and ii) the EU’s attempt to ‘balance’ the negotiations in 1995 by bringing in three relatively competitive sectors did not work out – it was precisely there that problems accumulated. It is critical that domestic regulators must be satisfied during and after the negotiations that their pursuit of health, safety, environment and consumer protection objectives will not be watered down in any way. Lessons drawn include, among others: MRAs are not about regulatory change (by definition), but if initial regulatory cleavages between trading partners are too wide, conditions become so restrictive that parties may regard them as a denial of the very purpose of the MRA. There are incentives to opt for alternatives in the market for the formalised designation of conformity assessment bodies in the MRA and these are often cheaper and faster, while equally qualified. Even in heavily regulated sectors such as medicines and medical devices, the narrow MRA has been superseded by near-global forms of effective cost-reducing cooperative (i.e. not treaty-based) regulatory alignment, a confirmation of the OECD approach that governments should think in terms of an entire spectrum of forms of regulatory cooperation.

La política, los partidos y las elecciones en Argentina 2015 : ¿Hacia un cambio en el campo político?

Este artículo propone ordenar el campo político argentino en torno a dos clivajes. El primero está representado por el clásico izquierda y derecha, el segundo por el peronismo y la posición "gorila" (antiperonista). Luego de una caracterización de los espacios ideológicos, usamos conceptos de la física (masa, fuerza y campo gravitacional) para analizar la dinámica de los partidos políticos y el futuro abierto luego de las últimas elecciones presidenciales de 2015

La política, los partidos y las elecciones en Argentina 2015 : ¿Hacia un cambio en el campo político?

Este artículo propone ordenar el campo político argentino en torno a dos clivajes. El primero está representado por el clásico izquierda y derecha, el segundo por el peronismo y la posición "gorila" (antiperonista). Luego de una caracterización de los espacios ideológicos, usamos conceptos de la física (masa, fuerza y campo gravitacional) para analizar la dinámica de los partidos políticos y el futuro abierto luego de las últimas elecciones presidenciales de 2015

La política, los partidos y las elecciones en Argentina 2015 : ¿Hacia un cambio en el campo político?

Este artículo propone ordenar el campo político argentino en torno a dos clivajes. El primero está representado por el clásico izquierda y derecha, el segundo por el peronismo y la posición "gorila" (antiperonista). Luego de una caracterización de los espacios ideológicos, usamos conceptos de la física (masa, fuerza y campo gravitacional) para analizar la dinámica de los partidos políticos y el futuro abierto luego de las últimas elecciones presidenciales de 2015

ISIS Success in Iraq: A Movement 40 Years in the Making

Thesis (Master's)--University of Washington, 2016-06

Endogenous Presentation of CD8+ T Cell Epitopes from Epstein-Barr Virus–encoded Nuclear Antigen 1

Epstein-Barr virus (EBV)-encoded nuclear antigen (EBNA)1 is thought to escape cytotoxic T lymphocyte (CTL) recognition through either self-inhibition of synthesis or by blockade of proteasomal degradation by the glycine-alanine repeat (GAr) domain. Here we show that EBNA1 has a remarkably varied cell type-dependent stability. However, these different degradation rates do not correspond to the level of major histocompatibility complex class I-restricted presentation of EBNA1 epitopes. In spite of the highly stable expression of EBNA1 in B cells, CTL epitopes derived from this protein are efficiently processed and presented to CD8(+) T cells. Furthermore, we show that EBV-infected B cells can readily activate EBNA1-specific memory T cell responses from healthy virus carriers. Functional assays revealed that processing of these EBNA1 epitopes is proteasome and transporter associated with antigen processing dependent. We also show that the endogenous presentation of these epitopes is dependent on the newly synthesized protein rather than the long-lived stable EBNA1. Based on these observations, we propose that defective ribosomal products, not the full-length antigen, are the primary source of endogenously processed CD8(+) T cell epitopes front EBNA1.

Ceramides reduce CD36 cell surface expression and oxidised LDL uptake by monocytes and macrophages

Oxidised LDL accumulates in macrophages following scavenger receptor (SR) uptake. The expression of the SR, CD36, is increased by oxidised LDL. The signalling molecule, ceramide, can modulate intracellular peroxides and increase lipid peroxidation. Ceramide also accumulates in atherosclerotic plaques. Thus, we have examined whether ceramide can modulate CD36 expression and function in human monocyte/macrophages. Addition of synthetic short chain ceramides or the action of sphingomyelinase to generate physiological long chain ceramides in situ caused significant reductions in CD36 expression by monocytes/macrophages which was not due to inhibition of mRNA expression. Inhibition of proteasomal degradation using lactacystin had no effect on CD36 expression, however, flow cytometric analysis of permeabilised cells suggested an intracellular trafficking blockade. Ceramide treated monocytes/macrophages showed dose dependent reduction in oxidised LDL uptake. Taken together, it is suggested that ceramide blocks the transport of CD36 to the membrane of monocytes/macrophages, thereby preventing uptake of oxidised LDL. © 2006 Elsevier Inc. All rights reserved.