Showing 181 - 190 of 733 Items
“Mayra Santos-Febres: El lenguaje de los cuerpos”. A Body of One’s Own: Conversations with Caribbean Women Writers
Date: 2008-01-01
Creator: Nadia V. Celis Salgado, Mayra Santos Febres
Access: Open access
Arginine methylation of yeast mRNA-binding protein Npl3 directly affects its function, nuclear export, and intranuclear protein interactions
Date: 2005-09-02
Creator: Anne E. McBride, Jeffrey T. Cook, Elizabeth A. Stemmler, Kate L. Rutledge, Kelly A., McGrath, Jeffrey A. Rubens
Access: Open access
- Arginine methylation can affect both nucleocytoplasmic transport and protein-protein interactions of RNA-binding proteins. These effects are seen in cells that lack the yeast hnRNP methyltransferase (HMT1), raising the question of whether effects on specific proteins are direct or indirect. The presence of multiple arginines in individual methylated proteins also raises the question of whether overall methylation or methylation of a subset of arginines affects protein function. We have used the yeast mRNA-binding protein Npl3 to address these questions in vivo. Matrix-assisted laser desorption/ionization Fourier transform mass spectrometry was used to identify 17 methylated arginines in Npl3 purified from yeast: whereas 10 Arg-Gly-Gly (RGG) tripeptides were exclusively dimethylated, variable levels off methylation were found for 5 RGG and 2 RG motif arginines. We constructed a set of Npl3 proteins in which subsets of the RGG arginines were mutated to lysine. Expression of these mutant proteins as the sole form of Npl3 specifically affected growth of a strain that requires Hmtl. Although decreased growth generally correlated with increased numbers of Arg-to-Lys mutations, lysine substitutions in the N terminus of the RGG domain showed more severe effects. Npl3 with all 15 RGG arginines mutated to lysine exited the nucleus independent of Hmtl, indicating a direct effect of methylation on Npl3 transport. These mutations also resulted in a decreased, methylation-independent interaction of Npl3 with transcription elongation factor Tho2 and inhibited Npl3 self-association. These results support a model in which arginine methylation facilitates Npl3 export directly by weakening contacts with nuclear proteins. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.
A two-hybrid assay to study protein interactions within the secretory pathway
Date: 2010-12-01
Creator: Danielle H. Dube, Bin Li, Ethan J. Greenblatt, Sadeieh Nimer, Amanda K., Raymond, Jennifer J. Kohler
Access: Open access
- Interactions of transcriptional activators are difficult to study using transcription-based two-hybrid assays due to potent activation resulting in false positives. Here we report the development of the Golgi two-hybrid (G2H), a method that interrogates protein interactions within the Golgi, where transcriptional activators can be assayed with negligible background. The G2H relies on cell surface glycosylation to report extracellularly on protein-protein interactions occurring within the secretory pathway. In the G2H, protein pairs are fused to modular domains of the reporter glycosyltransferase, Och1p, and proper cell wall formation due to Och1p activity is observed only when a pair of proteins interacts. Cells containing interacting protein pairs are identified by selectable phenotypes associated with Och1p activity and proper cell wall formation: cells that have interacting proteins grow under selective conditions and display weak wheat germ agglutinin (WGA) binding by flow cytometry, whereas cells that lack interacting proteins display stunted growth and strong WGA binding. Using this assay, we detected the interaction between transcription factor MyoD and its binding partner Id2. Interfering mutations along the MyoD:Id2 interaction interface ablated signal in the G2H assay. Furthermore, we used the G2H to detect interactions of the activation domain of Gal4p with a variety of binding partners. Finally, selective conditions were used to enrich for cells encoding interacting partners. The G2H detects protein-protein interactions that cannot be identified via traditional two-hybrid methods and should be broadly useful for probing previously inaccessible subsets of the interactome, including transcriptional activators and proteins that traffic through the secretory pathway. © 2010 Dube et al.
The Free-Trade Doctrine and Commercial Diplomacy of Condy Raguet
Date: 2011-05-11
Creator: Stephen Meardon
Access: Open access
- Condy Raguet (1784-1842) was the first Chargé d’Affaires from the United States to Brazil and a conspicuous author of political economy from the 1820s to the early 1840s. He contributed to the era’s free-trade doctrine as editor of influential periodicals, most notably The Banner of the Constitution. Before leading the free-trade cause, however, he was poised to negotiate a reciprocity treaty between the United States and Brazil, acting under the authority of Secretary of State and protectionist apostle Henry Clay. Raguet’s career and ideas provide a window into the uncertain relationship of reciprocity to the cause of free trade.
Learning by lending
Date: 2019-01-01
Creator: Matthew Botsch, Victoria Vanasco
Access: Open access
- This paper studies bank learning through repeated interactions with borrowers from a new perspective. To understand learning by lending, we adapt a methodology from labor economics to analyze how loan contract terms evolve as banks acquire new information about borrowers. We construct “proxy” variables for this information using data from borrowers’ out-of-sample, future credit performance. Due to the timing of their construction, banks could not have used these variables directly to price loans. We nonetheless find that these proxies increasingly predict loan prices as relationships progress, even after controlling for possible omitted variable bias. Our methodology provides strong evidence that: (a) bank learning affects loan prices, and (b) relationship benefits are heterogeneous. In particular, higher quality borrowers face differentially lower spreads as their relationship with lenders develop – and banks learn about their quality – while lower quality borrowers see loan prices increase and their loan amounts fall. We further find suggestive evidence that banks incorporate CEO-specific information into loan prices.
On kindleberger and hegemony: From berlin to MIT and back
Date: 2014-01-01
Creator: Stephen Meardon
Access: Open access
- The most conspicuous idea of Charles P. Kindleberger’s later career is the value of a single country acting as stabilizer of an international economy prone to instability. It runs through his widely read books, The World in Depression, 1929-1939 (1973), Manias, Panics, and Crashes (1978), A Financial History of Western Europe (1984), and kindred works. This essay traces Kindleberger’s attachment to the idea of “hegemonic stability” back to his tenure as chief of the State Department’s Division of German and Austrian Economic Affairs from 1945 to 1947 and adviser to the European Recovery Program from 1947 to 1948. In both capacities Kindleberger observed and participated indirectly in the 1948 monetary reform in Western Germany. In the 1990s, during his octogenary decade, he revisited the German monetary reform with a fellow participant, economist, and longtime friend, F. Taylor Ostrander. Their collaborative essay became Kindleberger’s effort to reclaim hegemonic stability theory from the scholars who developed it following his works of the 1970s and 1980s.
Wandering words: Tracing changes in words used by teacher tweeters over time
Date: 2017-01-01
Creator: Stephen Houser, Doris Santoro, Clare Bates Congdon, Jessica Hochman
Access: Open access
- Public school teachers in the United States are often constrained in terms of their ability to express their moral views on issues that affect their schools, classrooms, students, and teaching practices, but are able to express their ideas, concerns, and frustrations as private citizens using social media. Previously we developed the Tweet Capture and Clustering System (TCCS) in order to explore how teachers use Twitter, looking at word usage among a group of teacher tweeters, and attempting to find clusters of teachers who have similar patterns of word usage in their tweets. In the work reported here, we look at teacher tweeters across the 12 months of 2016, seeking to understand how the clusters and the words used in these clusters vary from month to month. In this initial look at the dynamics of the system, we see some evidence of word usage changing across the 12-month period. This initial work suggests that extending TCCS to have temporal topic tracing as a core capability will be a meaningful addition to of the system. Copyright held by the author(s).
Genetic interactions of yeast eukaryotic translation initiation factor 5a (eIF5A) reveal connections to poly(A)-binding protein and protein kinase C signaling
Date: 2002-03-14
Creator: Sandro R. Valentini, Jason M. Casolari, Carla C. Oliveira, Pamela A. Silver, Anne E., McBride
Access: Open access
- The highly conserved eukaryotic translation initiation factor eIF5A has been proposed to have various roles in the cell, from translation to mRNA decay to nuclear protein export. To further our understanding of this essential protein, three temperature-sensitive alleles of the yeast TIF51A gene have been characterized. Two mutant eIF5A proteins contain mutations in a proline residue at the junction between the two eIFSA domains and the third, strongest allele encodes a protein with a single mutation in each domain, both of which are required for the growth defect. The stronger tif51A alleles cause defects in degradation of short-lived mRNAs, supporting a role for this protein in mRNA decay. A multicopy suppressor screen revealed six genes, the overexpression of which allows growth of a tif51A-1 strain at high temperature; these genes include PAB1, PKC1, and PKC1 regulators WSC1, WSC2, and WSC3. Further results suggest that eIFSA may also be involved in ribosomal synthesis and the WSC/PKC1 signaling pathway for cell wall integrity or related processes.
Arginine methyltransferase affects interactions and recruitment of mRNA processing and export factors
Date: 2004-08-15
Creator: Michael C. Yu, François Bachand, Anne E. McBride, Suzanne Komili, Jason M., Casolari, Pamela A. Silver
Access: Open access
- Hmt1 is the major type I arginine methyltransferase in the yeast Saccharomyces cerevisiae and facilitates the nucleocytoplasmic transport of mRNA-binding proteins through their methylation. Here we demonstrate that Hmt1 is recruited during the beginning of the transcriptional elongation process. Hmt1 methylates Yra1 and Hrp1, two mRNA-binding proteins important for mRNA processing and export. Moreover, loss of Hmt1 affects interactions between mRNA-binding proteins and Tho2, a component of the TREX (transcription/export) complex that is important for transcriptional elongation and recruitment of mRNA export factors. Furthermore, RNA in situ hybridization analysis demonstrates that loss of Hmt1 results in slowed release of HSP104 mRNA from the sites of transcription. Genome-wide location analysis shows that Hmt1 is bound to specific functional gene classes, many of which are also bound by Tho2 and other mRNA-processing factors. These data suggest a model whereby Hmt1 affects transcriptional elongation and, as a result, influences recruitment of RNA-processing factors.
Metabolic Glycan Labeling-Based Screen to Identify Bacterial Glycosylation Genes
Date: 2020-12-11
Creator: Karen D. Moulton, Adedunmola P. Adewale, Hallie A. Carol, Sage A. Mikami, Danielle H., Dube
Access: Open access
- Bacterial cell surface glycans are quintessential drug targets due to their critical role in colonization of the host, pathogen survival, and immune evasion. The dense cell envelope glycocalyx contains distinctive monosaccharides that are stitched together into higher order glycans to yield exclusively bacterial structures that are critical for strain fitness and pathogenesis. However, the systematic study and inhibition of bacterial glycosylation enzymes remains challenging. Bacteria produce glycans containing rare sugars refractory to traditional glycan analysis, complicating the study of bacterial glycans and the identification of their biosynthesis machinery. To ease the study of bacterial glycans in the absence of detailed structural information, we used metabolic glycan labeling to detect changes in glycan biosynthesis. Here, we screened wild-type versus mutant strains of the gastric pathogen Helicobacter pylori, ultimately permitting the identification of genes involved in glycoprotein and lipopolysaccharide biosynthesis. Our findings provide the first evidence that H. pylori protein glycosylation proceeds via a lipid carrier-mediated pathway that overlaps with lipopolysaccharide biosynthesis. Protein glycosylation mutants displayed fitness defects consistent with those induced by small molecule glycosylation inhibitors. Broadly, our results suggest a facile approach to screen for bacterial glycosylation genes and gain insight into their biosynthesis and functional importance, even in the absence of glycan structural information.