Showing 721 - 730 of 2040 Items
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.
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.
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).
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.
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.
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.
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.
How Did Exchange Rates Affect Employment in US Cities?
Date: 2013-05-07
Creator: Yao Tang
Haifang Huang
Access: Open access
- We estimate the effects of real exchange rate movements on employment in US cities between 2003 and 2010. We explore the differences in the composition of local industries to construct city-specific changes in exchange rates and estimate their effects on local employment in manufacturing industries and in nonmanufacturing industries. Controlling for year and city fixed effects, we find that a depreciation of the US dollar increased local employment in the manufacturing industries, our proxy for the tradable sector. The depreciation also increased employment in the nonmanufacturing industries, the nontradable sector. Furthermore, the effects on nonmanufacturing employment were stronger in cities that had a higher fraction of manufacturing employment, indicating the exchange rate movements’ indirect effects through the manufacturing industries. We also consider an alternative definition of the tradable sector that is broadened to include five service industries. The findings are similar.
Interest group issue appeals: Evidence of issue convergence in senate and presidential elections, 2008-2014
Date: 2000-05-01
Creator: Michael M. Franz
Access: Open access
- Interest groups now play a prominent role in the air war. Their collective investment in election campaigns has skyrocketed in the aftermath of Citizens United. Yet questions remain about whether interest group advertising affects the content of the specific issues being discussed. Do groups enter campaigns and engage voters on the same issues as their candidate allies? Or does the presence of more advertisers introduce competitive issue streams? This paper examines ad buys in Senate elections between 2008 and 2014 and the presidential elections of 2008 and 2012. A primary goal of the paper is to uncover the effect of high and low levels of "issue convergence" on election outcomes. Strategists often express concern that too many voices on behalf of a candidate can weaken the impact of ads. One might expect that as convergence between a candidate and his or her allies goes up (meaning the issue content of the ad buys overlaps across advertisers), the impact of ads on votes will increase. Ad effects should be weaker when a candidate's ads discuss different issues from allied groups and party committees. The results, however, suggest that high rates of issue convergence are only weakly related to election outcomes (and not always in consistent ways).