Reliable, specific polyclonal and monoclonal antibodies are important tools in research and medicine. However, the discovery of antibodies against their targets in their native forms is difficult. Here, we present a novel method for discovery of antibodies against membrane proteins in their native configuration in mammalian cells. The method involves the co-expression of an antibody library in a population of mammalian cells that express the target polypeptide within a natural membrane environment on the cell surface. Cells that secrete a single-chain fragment variable (scFv) that binds to the target membrane protein thereby become self-labeled, enabling enrichment and isolation by magnetic sorting and FRET-based flow sorting. Library sizes of up to 109 variants can be screened, thus allowing campaigns of naïve scFv libraries to be selected against membrane protein antigens in a Chinese hamster ovary cell system. We validate this method by screening a synthetic naïve human scFv library against Chinese hamster ovary cells expressing the oncogenic target epithelial cell adhesion molecule and identify a panel of three novel binders to this membrane protein, one with a dissociation constant (KD) as low as 0.8 nm. We further demonstrate that the identified antibodies have utility for killing epithelial cell adhesion molecule–positive cells when used as a targeting domain on chimeric antigen receptor T cells. Thus, we provide a new tool for identifying novel antibodies that act against membrane proteins, which could catalyze the discovery of new candidates for antibody-based therapies.

Mammalian Asn-linked glycans are extensively processed as they transit the secretory pathway to generate diverse glycans on cell surface and secreted glycoproteins. Additional modification of the glycan core by α-1,6-fucose addition to the innermost GlcNAc residue (core fucosylation) is catalyzed by an α-1,6-fucosyltransferase (FUT8). The importance of core fucosylation can be seen in the complex pathological phenotypes of FUT8 null mice, which display defects in cellular signaling, development, and subsequent neonatal lethality. Elevated core fucosylation has also been identified in several human cancers. However, the structural basis for FUT8 substrate specificity remains unknown.Here, using various crystal structures of FUT8 in complex with a donor substrate analog, and with four distinct glycan acceptors, we identify the molecular basis for FUT8 specificity and activity. The ordering of three active site loops corresponds to an increased occupancy for bound GDP, suggesting an induced-fit folding of the donor-binding subsite. Structures of the various acceptor complexes were compared with kinetic data on FUT8 active site mutants and with specificity data from a library of glycan acceptors to reveal how binding site complementarity and steric hindrance can tune substrate affinity. The FUT8 structure was also compared with other known fucosyltransferases to identify conserved and divergent structural features for donor and acceptor recognition and catalysis. These data provide insights into the evolution of modular templates for donor and acceptor recognition among GT-B fold glycosyltransferases in the synthesis of diverse glycan structures in biological systems.

Broad-specificity glycoside hydrolases (GHs) contribute to plant biomass hydrolysis by degrading a diverse range of polysaccharides, making them useful catalysts for renewable energy and biocommodity production. Discovery of new GHs with improved kinetic parameters or more tolerant substrate-binding sites could increase the efficiency of renewable bioenergy production even further. GH5 has over 50 subfamilies exhibiting selectivities for reaction with β-(1,4)–linked oligo- and polysaccharides. Among these, subfamily 4 (GH5_4) contains numerous broad-selectivity endoglucanases that hydrolyze cellulose, xyloglucan, and mixed-linkage glucans. We previously surveyed the whole subfamily and found over 100 new broad-specificity endoglucanases, although the structural origins of broad specificity remained unclear. A mechanistic understanding of GH5_4 substrate specificity would help inform the best protein design strategies and the most appropriate industrial application of broad-specificity endoglucanases. Here we report structures of 10 new GH5_4 enzymes from cellulolytic microbes and characterize their substrate selectivity using normalized reducing sugar assays and MS. We found that GH5_4 enzymes have the highest catalytic efficiency for hydrolysis of xyloglucan, glucomannan, and soluble β-glucans, with opportunistic secondary reactions on cellulose, mannan, and xylan. The positions of key aromatic residues determine the overall reaction rate and breadth of substrate tolerance, and they contribute to differences in oligosaccharide cleavage patterns. Our new composite model identifies several critical structural features that confer broad specificity and may be readily engineered into existing industrial enzymes. We demonstrate that GH5_4 endoglucanases can have broad specificity without sacrificing high activity, making them a valuable addition to the biomass deconstruction toolset.

16 July 2020

4 September 2020

Priorities for implementing Ethiopia's national dialogue 11 May 2022 — 1:00PM TO 3:00PM Anonymous (not verified) 3 May 2022 Online

Experts discuss challenges and priorities in shaping an inclusive and effective national dialogue in Ethiopia.

Ethiopia is grappling with numerous contentious national issues – not least persistent conflict in several parts of the country – which underscore the need for large-scale dialogue and reconciliation efforts to address the country’s deep-rooted societal and political divisions. Ethiopia’s newly established National Dialogue Commission – whose 11 commissioners were appointed in February 2022 – has begun a four-phased process of preparations for a dialogue, with its initial stage focused on stakeholder engagement and local knowledge mobilization.

There are major challenges, however, in ensuring inclusivity amidst ongoing conflict and questions on how a country-wide process will sit alongside local dialogue initiatives and wider mediation and peacebuilding efforts. Linking the process to constitutional bodies will also be an important priority to ensure dialogue outcomes are effectively implemented.

At this public event, panellists will exchange perspectives on how to shape an effective national dialogue in Ethiopia, including priorities for building a credible National Dialogue Commission and the roles and responsibilities of other national, regional and local-level actors. They will also discuss key implementation mechanisms and long-term priorities for trust-building and cultivating a conducive environment for inclusive dialogue.

This webinar is part of a series of events and outputs on Ethiopia’s political transition.

This event will also be broadcast live on the Chatham House Africa Programme’s Facebook page.

Eight ways to build better African cities The World Today mhiggins.drupal 2 August 2022

Young professionals from across the continent tell Emmanuel Adegboye how city life could be improved: from high-speed rail to people-centred urban planning.

Ahmed Elsawy, 33, Director of Talent
Cairo, Egypt
We must amend employment law in Egypt to support individual contractors to match with the global demand for short-term and project-based assignments within the tech and service industries. While we have a new, decent education system, I think we should care more about foreign languages to have a higher rank when it comes to the global competition of skilled workers.

Iman Abubaker, 31, Urban Mobility Project Manager, WRI Africa
Addis Ababa, Ethiopia
Rapid urbanization and increased motorization have exacerbated the city’s urban challenges. Addis Ababa would benefit from safer street design and people-centred city planning. Urban amenities should be located within walking and cycling distances. For longer trips, the city needs to invest in improving the accessibility, safety, integration and multimodality of its public transport system. I would love to see more pockets of green spaces and parks all around the city. 

Bree, 31, Project Manager
Nairobi, Kenya
I have a love-hate relationship with Nairobi. I spent four years smack in the middle of the city while attending the University of Nairobi. Being in the middle of all the hustle and bustle made the transition to a sleepy-ish coastal town easy. I would happily trade matatus [shared taxis] for tuktuks any day. I do miss the conveniences that come with a big city like a 24-hour grocery store and delivery services on those lazy days.

Mfon Bassey, 30, Co-Founder, TalentX Africa
Lagos, Nigeria
The government should improve the road networks and public transport systems, because the common challenge most Lagosians face is commuting from point A to B without traffic. There are so many private cars on the road because the public transport system isn’t optimally efficient yet. Once you take away the commute time most workers spend just to get work done, we’ll surely have happier Lagosians.

Olga Kiconco, 32, Innovation Strategist
Kampala, Uganda
As one of Africa’s fastest-growing cities with a projected 112 per cent population growth by 2035, there are a number of critical changes that need to be made in preparation for this. Our leaders should embrace coherent policies that will catalyze socio-economic transformation. We need to hold them accountable for better infrastructure and delivery of public services, while taking personal responsibility to protect our environment against the prevalent threat of climate change.

Etienne Amougou, 30, Curator/Arts Project Manager
Yaounde, Cameroon
What would make Yaounde better would be a good ecosystem that provides more opportunities for young people. If it was possible, I would like to see the creation of more cultural spaces, like parks, zoos, cinemas and sport areas. Also, we could use a more effective approach to waste management – sometimes we have trash everywhere in the ’hood.

Valentino Fernandez, 23, Writer
Johannesburg, South Africa
 We need better transportation to bridge the inequality gap and allow the youth to access spaces to be inspired and create change. Apartheid spatial planning is still affecting us. People of colour were relegated to the outskirts of the city, and very little has changed. It’s virtually impossible to move out of your childhood home, which means you’re looking at a two-hour commute every morning and two more hours to get home. I would like a reliable, affordable, high-speed rail system.

Jean-Louis Mbaka, 34, Co-Founder and Director, Education at Kinshasa Digital
Kinshasa, DRC
Our youth must receive a sufficient education that is in line with the strategic requirements of their future workplaces. By 2030, more than 130 million jobs in Africa will require digital skills, according to the International Finance Corporation. To close the gap between the conventional educational system and the labour market, our organisation is providing training for digital jobs. Initiatives like ours must be supported if the current and next generations are to have the means for their economic and social advancement. Scaling up investments in vital facilities like the internet is also necessary.

Youth innovation can help shape the future of African cities Expert comment LToremark 16 August 2022

To meet the challenges of rapid urbanization, African governments must harness the potential of young innovators to help shape the future of African cities.

It is projected that 1.3 billion people will be living in Africa’s cities by 2050, an increase of almost 1 billion from today, and largely driven by young people migrating to urban centres in search of work. As the continent’s urban population grows, cities will need to adapt by nurturing new economic ecosystems to create jobs, while managing the environmental, social and political pressures that urbanization brings.

The evolution of Africa’s cities is critical for meeting the demands of its youth population and must be co-created with them. Africa’s young innovators are already proving to be an asset in shaping the future of African cities and, if they are allowed to flourish, they could be at the forefront of finding much-needed solutions to the continent’s vast urban challenges.

Growing tech hubs

African countries are increasingly benefitting from growth in technology ecosystems, which are often clustered within cities. There are currently more than 600 tech hubs helping to incubate innovative solutions across cities in Africa. Between 2015 and 2020, the number of start-ups receiving funding grew six times faster than the global average. In 2021 alone, start-ups raised over $4billion in funding – twice as much as in 2020.

But significant challenges remain. While the number of new start-ups is an encouraging indication of the entrepreneurialism and creativity of Africa’s youth, job creation on the level required will demand that they grow and scale up to generate more and higher quality jobs. Research on scaling up in Africa is sparse but research by Endeavor suggests that in Nairobi – one of Africa’s top tech ecosystems – only 5 per cent of companies are able to sustain growth of 20 per cent or more each year, yet they created 72 per cent of new jobs in the previous three years. For Africa to fully harness the potential of digital innovation, making cities the best place for young people to launch ideas and grow them into thriving businesses must become a priority policy for African governments. 

Barriers to scale

On the most basic level, business growth needs access to the services that make cities more liveable and help both urban residents and firms become more productive, such as healthcare, transport, water and sanitation. African cities already struggle to provide their residents – in particular the poorest and most vulnerable – with equitable, reliable, affordable and quality access to these services, in a sustainable manner. And these challenges will only get more acute as urban populations rise rapidly, often without any kind of integrated planning.

For example, an estimated 70-80 per cent of municipal solid waste in Africa is recyclable, yet only about 4 per cent is currently recycled, with more than 90 per cent of waste ending up in uncontrolled dumpsites and landfills. As Africa’s urban population grows, these conditions are likely to worsen – unless there is urgent action. New technology has the potential to help by creating a positive feedback loop between innovation, service delivery and growth. For example, to bridge the waste management gap, innovators are exploring various tech-enabled circular economy models. These solutions are often ground-breaking and have the potential to leapfrog traditional waste management infrastructure. Crucially, they are also formalizing a largely informal sector and creating new jobs.

Across the continent, start-ups like Kaltani, Mr Green Africa and Freetown Waste Transformers build processing facilities to turn waste into energy or reusable products, such as construction materials. Others, like Scrapays, Regenize and Soso Care, are helping households and businesses sell off their recycled materials for cash and virtual currencies or exchange them for critical services, such as micro health insurance premiums. Such start-ups help empower informal waste pickers or agents with tech-enabled tools and target low-income urban communities that would not normally prioritize recycling.

Help or hindrance from the top?

But Africa’s young people cannot do this alone – government decision-makers must become catalysts for entrepreneurial leadership. This requires nurturing a mindset that sees young innovators as Africa’s biggest resource, not a threat. While the importance of young people to Africa’s development is acknowledged in various high-level regional treaties, patterns of inhibition and outright hostility from political ‘elites’ suggest that the disruptive nature of technology start-ups and their access to significant capital through venture capital funding models – unlike existing rent-seeking business models with government control – threatens the political establishment.

The growing use of tech solutions also leads to increased transparency and efficiency of service delivery, which in turn leads to increased demand for government accountability and pressure to adopt more liberal policies. Until there is a shift towards catalysing entrepreneurial leadership, there is a stronger incentive for political elites to leverage their powers to co-opt successful technology businesses, or otherwise try to control them for political gain, than let them flourish. This shift in mindset will be critical to unlocking the full potential of Africa’s young innovators.

Africa’s strategic priorities and global role 27 January 2023 — 1:00PM TO 2:00PM Anonymous (not verified) 18 January 2023 Chatham House and Online

At this hybrid event, HE John Dramani Mahama, former president of the Republic of Ghana, will discuss his ideas on the key economic and governance reforms required for economic stability and prosperity across Africa.

Ghana recently became the fourth country, after Chad, Ethiopia and Zambia, to seek debt treatment under the G20 Common Framework in January 2023 – reflecting the culmination of a series of internal and external shocks affecting the wider region, including extreme weather events, the COVID-19 pandemic and the Russia-Ukraine crisis.

Prospects for economic recovery and growth, nevertheless, remain positive in many parts of the continent, with the African Development Bank (AfDB), for example, reforecasting economic growth of 5.5 per cent in East Africa in 2023. Coordinated reforms can help to deepen regional integration and promote long-term economic prosperity, particularly in light of Africa’s evolving regional economic governance structures, notably the fledgling African Continental Free Trade Area (AfCFTA) headquartered in Accra.

At this hybrid event, HE John Dramani Mahama, former president of the Republic of Ghana, will discuss his ideas on the key economic and governance reforms required for economic stability and prosperity across Africa. He will also discuss priorities for regional integration and Africa’s role and responsibilities in global economic governance.

Xiao-Ting Wen
Dec 17, 2020; 0:RA120.002119v1-mcp.RA120.002119
Research

Kyle Swovick
Dec 28, 2020; 0:RA120.002301v1-mcp.RA120.002301
Research

Alison M. Kurimchak
Dec 1, 2020; 19:2068-2089
Research

Peter Lasch
Dec 1, 2020; 19:2125-2138
Technological Innovation and Resources

This manuscript has been withdrawn by the Author.

Oxylipins are potent lipid mediators involved in a variety of physiological processes. Their profiling has the potential to provide a wealth of information regarding human health and disease and is a promising technology for translation into clinical applications. However, results generated by independent groups are rarely comparable, which increases the need for the implementation of internationally agreed upon protocols. We performed an interlaboratory comparison for the MS-based quantitative analysis of total oxylipins. Five independent laboratories assessed the technical variability and comparability of 133 oxylipins using a harmonized and standardized protocol, common biological materials (i.e., seven quality control plasmas), standard calibration series, and analytical methods. The quantitative analysis was based on a standard calibration series with isotopically labeled internal standards. Using the standardized protocol, the technical variance was within ±15% for 73% of oxylipins; however, most epoxy fatty acids were identified as critical analytes due to high variabilities in concentrations. The comparability of concentrations determined by the laboratories was examined using consensus value estimates and unsupervised/supervised multivariate analysis (i.e., principal component analysis and partial least squares discriminant analysis). Interlaboratory variability was limited and did not interfere with our ability to distinguish the different plasmas. Moreover, all laboratories were able to identify similar differences between plasmas. In summary, we show that by using a standardized protocol for sample preparation, low technical variability can be achieved. Harmonization of all oxylipin extraction and analysis steps led to reliable, reproducible, and comparable oxylipin concentrations in independent laboratories, allowing the generation of biologically meaningful oxylipin patterns.

Some cases of chylomicronemia are caused by autoantibodies against glycosylphosphatidylinositol-anchored HDL binding protein 1 (GPIHBP1), an endothelial cell protein that shuttles LPL to the capillary lumen. GPIHBP1 autoantibodies prevent binding and transport of LPL by GPIHBP1, thereby disrupting the lipolytic processing of triglyceride-rich lipoproteins. Here, we review the "GPIHBP1 autoantibody syndrome" and summarize clinical and laboratory findings in 22 patients. All patients had GPIHBP1 autoantibodies and chylomicronemia, but we did not find a correlation between triglyceride levels and autoantibody levels. Many of the patients had a history of pancreatitis, and most had clinical and/or serological evidence of autoimmune disease. IgA autoantibodies were present in all patients, and IgG4 autoantibodies were present in 19 of 22 patients. Patients with GPIHBP1 autoantibodies had low plasma LPL levels, consistent with impaired delivery of LPL into capillaries. Plasma levels of GPIHBP1, measured with a monoclonal antibody–based ELISA, were very low in 17 patients, reflecting the inability of the ELISA to detect GPIHBP1 in the presence of autoantibodies (immunoassay interference). However, GPIHBP1 levels were very high in five patients, indicating little capacity of their autoantibodies to interfere with the ELISA. Recently, several GPIHBP1 autoantibody syndrome patients were treated successfully with rituximab, resulting in the disappearance of GPIHBP1 autoantibodies and normalization of both plasma triglyceride and LPL levels. The GPIHBP1 autoantibody syndrome should be considered in any patient with newly acquired and unexplained chylomicronemia.

The organic anion transporters (OATs) and organic anion–transporting polypeptides (OATPs) belong to the solute carrier (SLC) transporter superfamily and play important roles in handling various endogenous and exogenous compounds of anionic charge. The OATs and OATPs are often implicated in drug therapy by impacting the pharmacokinetics of clinically important drugs and, thereby, drug exposure in the target organs or cells. Various mechanisms (e.g. genetic, environmental, and disease-related factors, drug-drug interactions, and food-drug interactions) can lead to variations in the expression and activity of the anion drug-transporting proteins of OATs and OATPs, possibly impacting the therapeutic outcomes. Previous investigations mainly focused on the regulation at the transcriptional level and drug-drug interactions as competing substrates or inhibitors. Recently, evidence has accumulated that cellular trafficking, post-translational modification, and degradation mechanisms serve as another important layer for the mechanisms underlying the variations in the OATs and OATPs. This review will provide a brief overview of the major OATs and OATPs implicated in drug therapy and summarize recent progress in our understanding of the post-translational modifications, in particular ubiquitination and degradation pathways of the individual OATs and OATPs implicated in drug therapy.

Studies in the yeast Saccharomyces cerevisiae have helped define mechanisms underlying the activity of the ubiquitin–proteasome system (UPS), uncover the proteasome assembly pathway, and link the UPS to the maintenance of cellular homeostasis. However, the spectrum of UPS substrates is incompletely defined, even though multiple techniques—including MS—have been used. Therefore, we developed a substrate trapping proteomics workflow to identify previously unknown UPS substrates. We first generated a yeast strain with an epitope tagged proteasome subunit to which a proteasome inhibitor could be applied. Parallel experiments utilized inhibitor insensitive strains or strains lacking the tagged subunit. After affinity isolation, enriched proteins were resolved, in-gel digested, and analyzed by high resolution liquid chromatography-tandem MS. A total of 149 proteasome partners were identified, including all 33 proteasome subunits. When we next compared data between inhibitor sensitive and resistant cells, 27 proteasome partners were significantly enriched. Among these proteins were known UPS substrates and proteins that escort ubiquitinated substrates to the proteasome. We also detected Erg25 as a high-confidence partner. Erg25 is a methyl oxidase that converts dimethylzymosterol to zymosterol, a precursor of the plasma membrane sterol, ergosterol. Because Erg25 is a resident of the endoplasmic reticulum (ER) and had not previously been directly characterized as a UPS substrate, we asked whether Erg25 is a target of the ER associated degradation (ERAD) pathway, which most commonly mediates proteasome-dependent destruction of aberrant proteins. As anticipated, Erg25 was ubiquitinated and associated with stalled proteasomes. Further, Erg25 degradation depended on ERAD-associated ubiquitin ligases and was regulated by sterol synthesis. These data expand the cohort of lipid biosynthetic enzymes targeted for ERAD, highlight the role of the UPS in maintaining ER function, and provide a novel tool to uncover other UPS substrates via manipulations of our engineered strain.

Renal Cell Carcinoma (RCC) is one of the most commonly diagnosed cancers worldwide with research efforts dramatically improving understanding of the biology of the disease. To investigate the role of the immune system in treatment-naïve clear cell Renal Cell Carcinoma (ccRCC), we interrogated the immune infiltrate in patient-matched ccRCC tumor samples, benign normal adjacent tissue (NAT) and peripheral blood mononuclear cells (PBMCs isolated from whole blood, focusing our attention on the myeloid cell infiltrate. Using flow cytometric, MS, and ExCYT analysis, we discovered unique myeloid populations in PBMCs across patient samples. Furthermore, normal adjacent tissues and ccRCC tissues contained numerous myeloid populations with a unique signature for both tissues. Enrichment of the immune cell (CD45⁺) fraction and subsequent gene expression analysis revealed a number of myeloid-related genes that were differentially expressed. These data provide evidence, for the first time, of an immunosuppressive and pro-tumorigenic role of myeloid cells in early, clinically localized ccRCC. The identification of a number of immune proteins for therapeutic targeting provides a rationale for investigation into the potential efficacy of earlier intervention with single-agent or combination immunotherapy for ccRCC.

Over the past decade, modern methods of MS (MS) have emerged that allow reliable, fast and cost-effective identification of pathogenic microorganisms. Although MALDI-TOF MS has already revolutionized the way microorganisms are identified, recent years have witnessed also substantial progress in the development of liquid chromatography (LC)-MS based proteomics for microbiological applications. For example, LC-tandem MS (LC-MS²) has been proposed for microbial characterization by means of multiple discriminative peptides that enable identification at the species, or sometimes at the strain level. However, such investigations can be laborious and time-consuming, especially if the experimental LC-MS² data are tested against sequence databases covering a broad panel of different microbiological taxa. In this proof of concept study, we present an alternative bottom-up proteomics method for microbial identification. The proposed approach involves efficient extraction of proteins from cultivated microbial cells, digestion by trypsin and LC–MS measurements. Peptide masses are then extracted from MS¹ data and systematically tested against an in silico library of all possible peptide mass data compiled in-house. The library has been computed from the UniProt Knowledgebase covering Swiss-Prot and TrEMBL databases and comprises more than 12,000 strain-specific in silico profiles, each containing tens of thousands of peptide mass entries. Identification analysis involves computation of score values derived from correlation coefficients between experimental and strain-specific in silico peptide mass profiles and compilation of score ranking lists. The taxonomic positions of the microbial samples are then determined by using the best-matching database entries. The suggested method is computationally efficient – less than 2 mins per sample - and has been successfully tested by a test set of 39 LC-MS¹ peak lists obtained from 19 different microbial pathogens. The proposed method is rapid, simple and automatable and we foresee wide application potential for future microbiological applications.

Endometrial carcinoma (EC) is the most common gynecologic malignancy in the United States, with limited effective targeted therapies. Endometrial tumors exhibit frequent alterations in protein kinases, yet only a small fraction of the kinome has been therapeutically explored. To identify kinase therapeutic avenues for EC, we profiled the kinome of endometrial tumors and normal endometrial tissues using Multiplexed Inhibitor Beads and Mass Spectrometry (MIB-MS). Our proteomics analysis identified a network of kinases overexpressed in tumors, including Serine/Arginine-Rich Splicing Factor Kinase 1 (SRPK1). Immunohistochemical (IHC) analysis of endometrial tumors confirmed MIB-MS findings and showed SRPK1 protein levels were highly expressed in endometrioid and uterine serous cancer (USC) histological subtypes. Moreover, querying large-scale genomics studies of EC tumors revealed high expression of SRPK1 correlated with poor survival. Loss-of-function studies targeting SRPK1 in an established USC cell line demonstrated SRPK1 was integral for RNA splicing, as well as cell cycle progression and survival under nutrient deficient conditions. Profiling of USC cells identified a compensatory response to SRPK1 inhibition that involved EGFR and the up-regulation of IGF1R and downstream AKT signaling. Co-targeting SRPK1 and EGFR or IGF1R synergistically enhanced growth inhibition in serous and endometrioid cell lines, representing a promising combination therapy for EC.

Les troubles gastro-intestinaux peuvent avoir un impact significatif sur la qualité de vie des patients. Ils engendrent en effet des symptômes variés et inconfortables allant de douleurs abdominales et nausées à des troubles plus graves comme les maladies inflammatoires chroniques de l’intestin. Quelles sont les principales pathologies rencontrées dans cette spécialité de la médecine ? À quel […]

L’article Quelles sont les principales pathologies en gastroentérologie ? est apparu en premier sur Ortho Doc France.

Ankylosing Spondylitis (AS) is a common, inflammatory rheumatic disease, which primarily affects the axial skeleton and is associated with sacroiliitis, uveitis and enthesitis. Unlike other autoimmune rheumatic diseases, such as rheumatoid arthritis or systemic lupus erythematosus, autoantibodies have not yet been reported to be a feature of AS. We therefore wished to determine if plasma from patients with AS contained autoantibodies and if so, characterize and quantify this response in comparison to patients with Rheumatoid Arthritis (RA) and healthy controls. Two high-density nucleic acid programmable protein arrays expressing a total of 3498 proteins were screened with plasma from 25 patients with AS, 17 with RA and 25 healthy controls. Autoantigens identified were subjected to Ingenuity Pathway Analysis in order to determine patterns of signalling cascades or tissue origin. 44% of patients with Ankylosing Spondylitis demonstrated a broad autoantibody response, as compared to 33% of patients with RA and only 8% of healthy controls. Individuals with AS demonstrated autoantibody responses to shared autoantigens, and 60% of autoantigens identified in the AS cohort were restricted to that group. The AS patients autoantibody responses were targeted towards connective, skeletal and muscular tissue, unlike those of RA patients or healthy controls. Thus, patients with AS show evidence of systemic humoral autoimmunity and multispecific autoantibody production. Nucleic Acid Programmable Protein Arrays constitute a powerful tool to study autoimmune diseases.

Complex protein glycosylation occurs through biosynthetic steps in the secretory pathway that create macro- and microheterogeneity of structure and function.  Required for all life forms, glycosylation diversifies and adapts protein interactions with binding partners that underpin interactions at cell surfaces and pericellular and extracellular environments. Because these biological effects arise from heterogeneity of structure and function, it is necessary to measure their changes as part of the quest to understand nature.  Quite often, however, the assumption behind proteomics that post-translational modifications are discrete additions that can be modeled using the genome as a template does not apply to protein glycosylation.  Rather, it is necessary to quantify the glycosylation distribution at each glycosite and to aggregate this information into a population of mature glycoproteins that exist in a given biological system.  To date, mass spectrometric methods for assigning singly glycosylated peptides are well-established.  But it is necessary to quantify glycosylation heterogeneity accurately in order to gauge the alterations that occur during biological processes.  The task is to quantify the glycosylated peptide forms as accurately as possible and then apply appropriate bioinformatics algorithms to the calculation of micro- and macro-similarities.  In this review, we summarize current approaches for protein quantification as they apply to this glycoprotein similarity problem.

Glycosylation is a prevalent, yet heterogeneous modification with a broad range of implications in molecular biology. This heterogeneity precludes enrichment strategies that can be universally beneficial for all glycan classes. Thus, choice of enrichment strategy has profound implications on experimental outcomes. Here we review common enrichment strategies used in modern mass spectrometry (MS)-based glycoproteomic experiments, including lectins and other affinity chromatographies, hydrophilic interaction chromatography (HILIC) and its derivatives, porous graphitic carbon (PGC), reversible and irreversible chemical coupling strategies, and chemical biology tools that often leverage bioorthogonal handles. Interest in glycoproteomics continues to surge as MS instrumentation and software improve, so this review aims to help equip researchers with necessary information to choose appropriate enrichment strategies that best complement these efforts.

Many cell surface and secreted proteins are modified by the covalent addition of glycans that play an important role in the development of multicellular organisms. These glycan modifications enable communication between cells and the extracellular matrix via interactions with specific glycan-binding lectins and the regulation of receptor-mediated signaling. Aberrant protein glycosylation has been associated with the development of several muscular diseases suggesting essential glycan- and lectin-mediated functions in myogenesis and muscle development but our molecular understanding of the precise glycans, catalytic enzymes and lectins involved remain only partially understood. Here, we quantified dynamic remodeling of the membrane-associated proteome during a time-course of myogenesis in cell culture. We observed wide-spread changes in the abundance of several important lectins and enzymes facilitating glycan biosynthesis. Glycomics-based quantification of released N-linked glycans confirmed remodeling of the glycome consistent with the regulation of glycosyltransferases and glycosidases responsible for their formation including a previously unknown di-galactose-to-sialic acid switch supporting a functional role of these glycoepitopes in myogenesis. Furthermore, dynamic quantitative glycoproteomic analysis with multiplexed stable isotope labelling and analysis of enriched glycopeptides with multiple fragmentation approaches identified glycoproteins modified by these regulated glycans including several integrins and growth factor receptors. Myogenesis was also associated with the regulation of several lectins most notably the up-regulation of galectin-1 (LGALS1). CRISPR/Cas9-mediated deletion of Lgals1 inhibited differentiation and myotube formation suggesting an early functional role of galectin-1 in the myogenic program. Importantly, similar changes in N-glycosylation and the up-regulation of galectin-1 during postnatal skeletal muscle development were observed in mice. Treatment of new-born mice with recombinant adeno-associated viruses to overexpress galectin-1 in the musculature resulted in enhanced muscle mass. Our data form a valuable resource to further understand the glycobiology of myogenesis and will aid the development of intervention strategies to promote healthy muscle development or regeneration.

Regulation of gene expression is essential for the functioning of all eukaryotic organisms. Understanding gene expression regulation requires determining which proteins interact with regulatory elements in chromatin. Mass spectrometry-based analysis of chromatin has emerged as a powerful tool to identify proteins associated with gene regulation, as it allows studying protein function and protein complex formation in their in vivo chromatin-bound context. Total chromatin isolated from cells can be directly analysed using mass spectrometry or further fractionated into transcriptionally active and inactive chromatin prior to MS-based analysis. Newly formed chromatin that is assembled during DNA replication can also be specifically isolated and analysed. Furthermore, capturing specific chromatin domains facilitates the identification of previously unknown transcription factors interacting with these domains. Finally, in recent years, advances have been made towards identifying proteins that interact with a single genomic locus of interest. In this review, we highlight the power of chromatin proteomics approaches and how these provide complementary alternatives compared to conventional affinity purification methods. Furthermore, we discuss the biochemical challenges that should be addressed to consolidate and expand the role of chromatin proteomics as a key technology in the context of gene expression regulation and epigenetics research in health and disease.

Antibodies play essential roles in both diagnostics and therapeutics. Epitope mapping is essential to understand how an antibody works and to protect intellectual property. Given the millions of antibodies for which epitope information is lacking, there is a need for high-throughput epitope mapping. To address this, we developed a strategy, Antibody binding epitope Mapping (AbMap), by combining a phage displayed peptide library with next generation sequencing. Using AbMap, profiles of the peptides bound by 202 antibodies were determined in a single test, and linear epitopes were identified for >50% of the antibodies. Using spike protein (S1 and S2)-enriched antibodies from the convalescent serum of one COVID-19 patient as the input, both linear and conformational epitopes of spike protein specific antibodies were identified. We defined peptide-binding profile of an antibody as the Binding Capacity (BiC). Conceptually, the BiC could serve as a systematic and functional descriptor of any antibody. Requiring at least one order of magnitude less time and money to map linear epitopes than traditional technologies, AbMap allows for high-throughput epitope mapping and creates many possibilities.

To identify novel autoantibodies of Takayasu arteritis (TAK) using HuProt array-based approach. A two-phase approach was adopted. In Phase I, serum samples collected from 40 TAK patients, 15 autoimmune disease patients, and 20 healthy subjects were screened to identify TAK-specific autoantibodies using human protein (HuProt) arrays. In Phase II, the identified candidate autoantibodies were validated with TAK-focused arrays using an additional cohort comprised of 109 TAK patients, 110 autoimmune disease patients, and 96 healthy subjects. Subsequently, the TAK-specific autoantibodies validated in Phase II were further confirmed using Western blot analysis. We identified and validated eight autoantibodies as potential TAK-specific diagnostic biomarkers, including anti-SPATA7, -QDPR, -SLC25A2, -PRH2, -DIXDC1, -IL17RB, -ZFAND4, and -NOLC1 antibodies, with AUC of 0.803, 0.801, 0.780, 0.696, 0.695, 0.678, 0.635 and 0.613, respectively. SPATA7 could distinguish TAK from healthy and disease controls with 73.4% sensitivity at 85.4% specificity, while QDPR showed 71.6% sensitivity at 86.4% specificity. SLC25A22 showed the highest sensitivity of 80.7%, but at lower specificity of 67.0%. In addition, PRH2, IL17RB and NOLC1 showed good specificities of 88.3%, 85.9% and 86.9%, respectively, but at lower sensitivities (<50%). Finally, DIXDC1 and ZFAND4 showed moderate performance as compared with the other autoantibodies. Using a decision tree model, we could reach a specificity of 94.2% with AUC of 0.843, a significantly improved performance as compared to that by each individual biomarker. The performance of three autoantibodies, namely anti-SPATA7, -QDPR and -PRH2, were successfully confirmed with Western blot analysis. Using this two-phase strategy, we identified and validated eight novel autoantibodies as TAK–specific biomarker candidates, three of which could be readily adopted in a clinical setting.

Cells continually degrade and replace damaged proteins. However, the high energetic demand of protein turnover generates reactive oxygen species (ROS) that compromise the long-term health of the proteome. Thus, the relationship between aging, protein turnover and energetic demand remains unclear. Here, we used a proteomic approach to measure rates of protein turnover within primary fibroblasts isolated from a number of species with diverse lifespans including the longest-lived mammal, the bowhead whale. We show that organismal lifespan is negatively correlated with turnover rates of highly abundant proteins. In comparison to mice, cells from long-lived naked mole rats have slower rates of protein turnover, lower levels of ATP production and reduced ROS levels. Despite having slower rates of protein turnover, naked mole rat cells tolerate protein misfolding stress more effectively than mouse cells. We suggest that in lieu of rapid constitutive turnover, long-lived species may have evolved more energetically efficient mechanisms for selective detection and clearance of damaged proteins.

Recent advances in MS-based proteomics have vastly increased the quality and scope of biological information that can be derived from human samples. These advances have rendered current workflows increasingly applicable in biomedical and clinical contexts. As proteomics is poised to take an important role in the clinic, associated ethical responsibilities increase in tandem with the impact on the health, privacy, and well-being of individuals. Here we conducted and report a systematic literature review of ethical issues in clinical proteomics. We add our perspectives from a background of bioethics, the results of our accompanying paper extracting individual-sensitive results from patient samples, and the literature addressing similar issues in genomics. The spectrum of potential issues ranges from patient re-identification to incidental findings of clinical significance. The latter can be divided into actionable and unactionable findings. Some of these have the potential to be employed in discriminatory or privacy-infringing ways. However, incidental findings may also have great positive potential. A plasma proteome profile, for instance, could inform on the general health or disease status of an individual regardless of the narrow diagnostic question that prompted it. We suggest that early discussion of ethical issues in clinical proteomics is important to ensure that eventual regulations reflect the considered judgment of the community as well as to anticipate opportunities and problems that may arise as the technology matures further.

Gender-smart Procurement: Policies for Driving Change Research paper sysadmin 14 December 2017

Governments should use public procurement policy as a strategic lever to accelerate gender-inclusive economic growth through the application of state spending power.

• Governments need to rethink public procurement policy. They need to use it as a strategic lever to accelerate gender-inclusive economic growth through the application of state spending power, while maintaining rigorous governance standards. Reform of public procurement to make it more gender-inclusive could create a ‘diversity dividend’ through increased job creation and economic growth. Gender-smart procurement policies could also mitigate economic and business risk by rendering supply chains more diverse.
• In 2014, G20 members agreed to reduce the gender gap in the labour market by 25 per cent by 2025. Procurement policy is one of the most powerful tools governments have to achieve this goal. All G20 members, regardless of the differences in their legal frameworks, can implement measures that will increase the ability of women to benefit from procurement policy.
• Public procurement accounts for around one-fifth of global gross domestic product (GDP). It is estimated that women entrepreneurs supply only 1 per cent of this market. Women’s businesses face considerable barriers to accessing procurement tenders and winning procurement contracts. The inadequate design of many procurement processes prevents more inclusive gender outcomes for citizens. Governments should redefine procurement policies to make explicit the requirement that increasing women’s workforce participation, through greater use of female suppliers, is a key objective when selecting bids for procurement contracts.
• Through the use of policy and spending levers, governments can play four primary roles in encouraging procurement from enterprises owned by women, or from businesses committed to promoting female labour participation. These roles are:
  - To direct reforms of government procurement – reviewing procurement policies and practices to ensure sustainable and inclusive procurement;
  - To reduce barriers to women’s participation in the economy – creating the support mechanisms to ensure an environment in which businesses owned by women can flourish;
  - To help scale up gender-smart procurement in the private sector – expanding government’s role in encouraging private companies to spend more of their procurement budgets with women’s businesses; and
  - To encourage increased transparency on the issues – creating and sharing procurement databases and lessons learned, especially at the regional level.
• Companies can also benefit from having more diverse supply chains and volunteering for accreditation schemes. They can start conversations with government about national regulation that encourages diversity in procurement, leading by example.
• The G20 should set measurable and time-bound targets in the area of gender-smart procurement, to build on the momentum of UN reforms and incorporate good practice in supply chain management.

Prices, Products and Priorities: Meeting Refugees’ Energy Needs in Burkina Faso and Kenya Other resource sysadmin 24 January 2018

As the number of displaced people increases, and aid budgets come under further pressure, the imperative to identify cost-effective and sustainable solutions for delivering energy to refugees is more pressing than ever.

This paper examines the issue of energy and displacement in detail, using insights from refugees in camps in Burkina Faso and Kenya. It seeks to promote a better understanding of their energy needs, priorities and preferences, and explores how increased access to energy might help to achieve lasting impact in the two camps surveyed. The paper is based on primary research from the Goudoubo camp in Burkina Faso and the Kakuma I camp in Kenya, but the analysis and conclusions are pertinent in the wider context of camps for forcibly displaced people.

Summary points

• There is a low level of energy access in the refugee camps of Kakuma I and Goudoubo, which contributes to poverty and hampers relief and development efforts. Trying to meet basic cooking, lighting and phone-charging needs is costly for refugees, consuming a significant share of stretched monthly budgets.
• The predominant cooking solution consists of basic improved cookstoves burning wood and charcoal. The ‘three-stone fire’ method also remains commonplace. Three out of five families in Kakuma I report health problems due to smoke from cookstoves.
• Street lighting is a high priority for residents, due to concerns about security and safety in camps. In Goudoubo, 86 per cent of survey respondents said that more household members would go out after dark if there were better public lighting.
• A significant proportion of refugees would pay for cleaner and more efficient energy technologies, but many lack the financial resources required, and the development of markets for such products remains partially contingent on sustained financial support.
• There is a need for a diversity of energy technologies that give varying levels and qualities of service; a ‘one size fits all’ approach is inappropriate if universal access to sustainable energy is to be achieved.
• Clean cookstoves and fuels (LPG, ethanol, biogas, etc.) are in high demand, but require much greater investment if they are to be introduced at scale. Solid biomass and improved cookstoves will continue to be important cooking solutions in Kakuma I and Goudoubo, as well as in other refugee camps. A shift to more efficient cooking can be achieved at little or no extra cost for the significant proportion of people who still cook on three-stone fires.
• Users of quality-verified household solar products spend dramatically less on light and power than do people using inferior technologies. Strong brand recognition and a high willingness to pay indicate a large market and a significant opportunity for the solar private sector.
• Centralized electricity supply solutions – mini-grids or grid connections – are more economic than multiple standalone diesel generators. The current piecemeal and ad hoc approach, with each facility managing its own power supply, is inherently wasteful. Greater coordination among humanitarian clusters is required so that centralized solutions can be assessed, designed, financed and implemented.
• Collecting data on energy expenditure and use, as well as quantification of the wide ranging impacts of improved technologies, is necessary to build a compelling case for investment in electricity infrastructure. In addition, engaging refugees on their needs, preferences and willingness to pay can improve the sustainability and impact of energy interventions.
• Private-sector and market development approaches offer long-term, cost-effective solutions for refugees and can also benefit host communities. As the number of displaced people in the world increases, and as aid budgets come under further pressure, the imperative to identify cost-effective and sustainable solutions is more pressing than ever.

Chatham House is a part of the Moving Energy Initiative, a consortium working towards clean energy for refugees. For more information visit movingenergy.earth

Dance of the Trillions: Developing Countries and Global Finance Book sysadmin 6 July 2018

David Lubin tells the story of what makes money flow from high-income countries to lower-income ones; what makes it flow out again; and how developing countries have sought protection against the volatility of international capital flows.

Selected by the Financial Times as one of the best economics books of 2018, Dance of the Trillions traces an arc from the 1970s, when developing countries first gained access to international financial markets, to the present day.

Underlying this story is a discussion of how the relationship between developing countries and global finance appears to be moving from one governed by the ‘Washington Consensus’ to one more likely to be shaped by Beijing.

This book is part of the Insights series.

Praise for Dance of the Trillions

About the author

David Lubin is managing director and head of emerging markets economics at Citi, an American bank, where he is responsible for a team of more than 30 economists in 15 locations globally.

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• UK (via Amazon)
• Rest of world (via Brookings Institution Press)
• Students (via Browns Books)

Proportionality in the Conduct of Hostilities: The Incidental Harm Side of the Assessment Research paper sysadmin 6 December 2018

Clarification of international humanitarian law is important in ensuring compliance with the rule of proportionality, but a culture of compliance within armed forces and groups is also crucial.

Summary

• Military operations are taking place with increasing frequency in densely populated areas. Such operations result in loss of life and harm to civilians, as well as damage to civilian objects, (including infrastructure providing essential services). In order to protect civilians, it is imperative that armed forces and groups comply with the rules of international humanitarian law on the conduct of hostilities, including the rule of proportionality.
• The rule of proportionality prohibits attacks which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated. This research paper analyses the key steps that belligerents must take to give effect to the rule, with a particular focus on one side of proportionality assessments – the expected incidental harm.
• Those undertaking proportionality assessments before or during an attack must consider whether the expected harm will be caused by the attack, and whether that harm could be expected (that is, was it reasonably foreseeable).
• For the purpose of proportionality assessments, injury to civilians includes disease, and there is no reason in principle to exclude mental harm, even though it is currently challenging to identify and quantify it. Damage to civilian objects includes damage to elements of the natural environment.
• Once the incidental harm to be considered has been identified, a value or weight must be assigned to it. This is then balanced against the value or weight of the military advantage anticipated from the attack to determine whether the harm would be excessive.
• In the determination of whether the expected incidental harm would be excessive compared to the anticipated military advantage, ‘excessive’ is a wide but not indeterminate standard.
• Belligerents should develop methodologies so that those planning and deciding attacks are provided with all necessary information on expected incidental harm, and to assist them in assigning weight to the incidental harm to be considered.
• If it becomes apparent that the rule of proportionality will be contravened, the attack in question must be cancelled or suspended.
• Clarification of the law is important in ensuring compliance with the rule of proportionality, but a culture of compliance within armed forces and groups, inculcated by their leaders, is also crucial.

The Chatham House Sustainable Laboratories Initiative: Prior Assessment Tool Other resource sysadmin 14 June 2019

Laboratories are critical for supporting effective infectious disease surveillance and outbreak response. This tool is meant to help structure a conversation between funding partners and recipient countries on how to most effectively establish or repurpose laboratories in low-resource environments.

Introduction

Laboratories are critical for supporting effective infectious disease surveillance and outbreak response, and lack of adequate laboratory capacity is a global challenge. As part of global health security initiatives, cooperative threat reduction efforts and international development programmes, sophisticated laboratories have been provided to mitigate biological threats and bolster a country’s capacity for detection, diagnosis and storage of high-consequence pathogens. Very often, these use the assumptions, standards and templates applied in high-income countries. However, it can be difficult or even impossible to sustain these facilities in low-resource environments. There can sometimes be limited local technical capacity and capability, which can result in a high reliance on imported expertise, skills, equipment and other resources. Sustainability can therefore be hard to achieve. In addition, when a funding partner withdraws, the laboratories can become disused, foundering without the trained personnel and financial resources to sustain them.

To help address this situation, a proposal gaining increasing support internationally is to adopt an approach based on a local risk assessment, whereby laboratories are appropriately and optimally tailored to the local risks and to the resources available, both in the short and longer term, without compromising biosafety and biosecurity.

A Chatham House workshop was convened in Abuja, Nigeria, in 2018 to explore what West African countries would find most appropriate in terms of building laboratory capacity, what the main challenges have been so far, and what needs to be done to improve the sustainability of laboratories in the region. It emerged that there was a need for a more structured conversation between the funding partner and recipient country early in the process – prior to embarking on the detailed planning phase for the establishment or repurposing of a laboratory. This should involve careful consideration and an assessment of existing and planned capacity, needs and contextual issues, together with proposals for how to address the issues revealed, so that any ensuing laboratory demonstrably supports the national strategy and therefore flourishes.

Subsidies and Sustainable Agriculture: Mapping the Policy Landscape Research paper sysadmin 10 December 2019

Agricultural subsidies shape production and consumption patterns, with potentially significant effects on poverty, nutrition and other sustainability concerns. This paper maps the different types of support provided by governments to the agricultural sector, and highlights some of the complex political economy dynamics that underpin the relevant policies.

Summary

• Agricultural subsidies, a mainstay of government policy, have a large part in shaping production and consumption patterns, with potentially significant effects as regards poverty, food security, nutrition, and other sustainability concerns such as climate change, land use practices and biodiversity.
• There are multiple types of direct and indirect support provided by governments to various actors in the agricultural sector; and in terms of political economy, there are complex dynamics underpinning the policies that sustain these subsidies.
• Overall, subsidies targeting producers have the most significant effect on production, and the greater trade-distorting effect. These subsidies promote domestic production and discourage imports, leading to overproduction that is largely disposed of on the international market, with the help of export subsidies. This can tend to intensify negative environmental agricultural practices, such as cultivating marginal land, unsustainable types of intensification, or incentivizing excessive pesticide and fertilizer use.
• On the other hand, producer subsidies that are not tied to output of a specific commodity (i.e. delinked) have far fewer distorting impacts and could help to deliver sustainable outcomes. For example, this type of subsidies can require crop diversification or be linked to conservation of permanent grassland.
• Subsidies that enable transfers to consumers, for example through food stamp programmes, also serve to delink production from consumption, can foster healthier diets, can play an important role in delivering food accessibility and security among low-income groups, and can represent one of the less trade-distorting subsidies.
• If subsidies are to be reformed to help promote healthier diets and encourage more sustainable production, it is essential to understand not only the type and amount of support that key countries provide, but also the domestic dynamics that can shape such policies.
• While price support, input subsidies or investment aids remain the central pillars of programmes in large developing countries such as Brazil, China or India, other economies – notably including the EU and Japan – focus on direct payments, support for general services and set-aside schemes, as well as significant border protection. The US, for its part, has tended to focus on subsidized insurance schemes and food programmes for poorer consumers.
• If subsidies are to deliver policy objectives, their design and implementation should delink production from consumption. For example, consumer subsidies designed to deliver nutrition and food security, or payments for environmental services to enable more environmentally friendly production systems, could prove to be the most effective, least trade-distorting means of achieving more sustainable and equitable agricultural production.
• The political economy of food means that the removal of subsidies is often highly sensitive, and tends to be met with significant resistance. However, reform that delinks support from production through a gradual transition process could ultimately prove successful in delivering effective subsidy schemes.
• Effective subsidy schemes must by design be truly result- and performance-based, supported by robust and objective indicators. At the same time, engaging multiple actors along key commodity value chains – including leading importing and exporting countries, traders and transporters – could lead to the development of international, commodity-specific arrangements that are able to deliver effective nutrition and sustainability goals.

Secrets and Spies: UK Intelligence Accountability After Iraq and Snowden Book sysadmin 15 January 2020

How can democratic governments hold intelligence and security agencies to account when what they do is largely secret? Jamie Gaskarth explores how intelligence professionals view accountability in the context of 21st century politics.

Using the UK as a case study, this book provides the first systematic exploration of how accountability is understood inside the secret world. It is based on new interviews with current and former UK intelligence practitioners, as well as extensive research into the performance and scrutiny of the UK intelligence machinery.

The result is the first detailed analysis of how intelligence professionals view their role, what they feel keeps them honest, and how far external overseers impact on their work.

The UK gathers material that helps inform global decisions on such issues as nuclear proliferation, terrorism, transnational crime, and breaches of international humanitarian law. On the flip side, the UK was a major contributor to the intelligence failures leading to the Iraq war in 2003, and its agencies were complicit in the widely discredited U.S. practices of torture and ‘rendition’ of terrorism suspects. UK agencies have come under greater scrutiny since those actions, but it is clear that problems remain.

Secrets and Spies is the result of a British Academy funded project (SG151249) on intelligence accountability. The book is published as part of the Insights series.

Praise for Secrets and Spies

About the author

Jamie Gaskarth is Professor of Foreign Policy and International Relations at The Open University. He was previously senior lecturer at the University of Birmingham where he taught strategy and decision-making. His research focused on the ethical dilemmas of leadership and accountability in intelligence, foreign policy, and defence. He is author/editor or co-editor of six books and served on the Academic Advisory panel for the 2015 UK National Security Strategy and Strategic Defence and Security Review.

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• UK (via Amazon)
• Rest of world (via Brookings Institution Press)
• Students (via Browns Books)

Centenary Series: Exploring the International Affairs Archive dora.popova 14 September 2020

International Affairs has been a central part of the institute’s history, both as a record of speeches made by dignitaries such as Mahatma Gandhi and Henry Kissinger, and as a forum for policy-relevant academic research.

Delving into the International Affairs archive brings out stories behind some of the most significant players of the last century.

The faithful segregation, or “partition,” of many low-copy number bacterial plasmids is driven by plasmid-encoded ATPases that are represented by the P1 plasmid ParA protein. ParA binds to the bacterial nucleoid via an ATP-dependent nonspecific DNA (nsDNA)-binding activity, which is essential for partition. ParA also has a site-specific DNA-binding activity to the par operator (parOP), which requires either ATP or ADP, and which is essential for it to act as a transcriptional repressor but is dispensable for partition. Here we examine how DNA binding by ParA contributes to the relative distribution of its plasmid partition and repressor activities, using a ParA with an alanine substitution at Arg351, a residue previously predicted to participate in site-specific DNA binding. In vivo, the parAR351A allele is compromised for partition, but its repressor activity is dramatically improved so that it behaves as a “super-repressor.” In vitro, ParAR351A binds and hydrolyzes ATP, and undergoes a specific conformational change required for nsDNA binding, but its nsDNA-binding activity is significantly damaged. This defect in turn significantly reduces the assembly and stability of partition complexes formed by the interaction of ParA with ParB, the centromere-binding protein, and DNA. In contrast, the R351A change shows only a mild defect in site-specific DNA binding. We conclude that the partition defect is due to altered nsDNA binding kinetics and affinity for the bacterial chromosome. Furthermore, the super-repressor phenotype is explained by an increased pool of non-nucleoid bound ParA that is competent to bind parOP and repress transcription.

In eukaryotic DNA replication, DNA polymerase ε (Polε) is responsible for leading strand synthesis, whereas DNA polymerases α and δ synthesize the lagging strand. The human Polε (hPolε) holoenzyme is comprised of the catalytic p261 subunit and the noncatalytic p59, p17, and p12 small subunits. So far, the contribution of the noncatalytic subunits to hPolε function is not well understood. Using pre-steady-state kinetic methods, we established a minimal kinetic mechanism for DNA polymerization and editing catalyzed by the hPolε holoenzyme. Compared with the 140-kDa N-terminal catalytic fragment of p261 (p261N), which we kinetically characterized in our earlier studies, the presence of the p261 C-terminal domain (p261C) and the three small subunits increased the DNA binding affinity and the base substitution fidelity. Although the small subunits enhanced correct nucleotide incorporation efficiency, there was a wide range of rate constants when incorporating a correct nucleotide over a single-base mismatch. Surprisingly, the 3'→5' exonuclease activity of the hPolε holoenzyme was significantly slower than that of p261N when editing both matched and mismatched DNA substrates. This suggests that the presence of p261C and the three small subunits regulates the 3'→5' exonuclease activity of the hPolε holoenzyme. Together, the 3'→5' exonuclease activity and the variable mismatch extension activity modulate the overall fidelity of the hPolε holoenzyme by up to 3 orders of magnitude. Thus, the presence of p261C and the three noncatalytic subunits optimizes the dual enzymatic activities of the catalytic p261 subunit and makes the hPolε holoenzyme an efficient and faithful replicative DNA polymerase.

The Phillies continued to bolster their infield depth on Friday by signing versatile veteran Sean Rodriguez to a Minor League contract with an invite to big league Spring Training, MLB.com has learned.

The Phillies acquired All-Star catcher J.T. Realmuto from the Marlins on Thursday for catcher Jorge Alfaro, right-hander Sixto Sanchez, left-hander Will Stewart and $250,000 in international bonus slot money, the latest move in a busy and ambitious offseason for a team eager to return to the postseason.