Suppression of gene silencing: A general strategy used by diverse DNA and RNA viruses of plants

In transgenic and nontransgenic plants, viruses are both initiators and targets of a defense mechanism that is similar to posttranscriptional gene silencing (PTGS). Recently, it was found that potyviruses and cucumoviruses encode pathogenicity determinants that suppress this defense mechanism. Here, we test diverse virus types for the ability to suppress PTGS. Nicotiana benthamiana exhibiting PTGS of a green fluorescent protein transgene were infected with a range of unrelated viruses and various potato virus X vectors producing viral pathogenicity factors. Upon infection, suppression of PTGS was assessed in planta through reactivation of green fluorescence and confirmed by molecular analysis. These experiments led to the identification of three suppressors of PTGS and showed that suppression of PTGS is widely used as a counter-defense strategy by DNA and RNA viruses. However, the spatial pattern and degree of suppression varied extensively between viruses. At one extreme, there are viruses that suppress in all tissues of all infected leaves, whereas others are able to suppress only in the veins of new emerging leaves. This variation existed even between closely related members of the potexvirus group. Collectively, these results suggest that virus-encoded suppressors of gene silencing have distinct modes of action, are targeted against distinct components of the host gene-silencing machinery, and that there is dynamic evolution of the host and viral components associated with the gene-silencing mechanism.

Recognition of Yeast mRNAs as “Nonsense Containing” Leads to Both Inhibition of mRNA Translation and mRNA Degradation: Implications for the Control of mRNA Decapping

A critical step in the degradation of many eukaryotic mRNAs is a decapping reaction that exposes the transcript to 5′ to 3′ exonucleolytic degradation. The dual role of the cap structure as a target of mRNA degradation and as the site of assembly of translation initiation factors has led to the hypothesis that the rate of decapping would be specified by the status of the cap binding complex. This model makes the prediction that signals that promote mRNA decapping should also alter translation. To test this hypothesis, we examined the decapping triggered by premature termination codons to determine whether there is a down-regulation of translation when mRNAs were recognized as “nonsense containing.” We constructed an mRNA containing a premature stop codon in which we could measure the levels of both the mRNA and the polypeptide encoded upstream of the premature stop codon. Using this system, we analyzed the effects of premature stop codons on the levels of protein being produced per mRNA. In addition, by using alterations either in cis or in trans that inactivate different steps in the recognition and degradation of nonsense-containing mRNAs, we demonstrated that the recognition of a nonsense codon led to a decrease in the translational efficiency of the mRNA. These observations argue that the signal from a premature termination codon impinges on the translation machinery and suggest that decapping is a consequence of the change in translational status of the mRNA.

Negative Factor from SIV Binds to the Catalytic Subunit of the V-ATPase to Internalize CD4 and to Increase Viral Infectivity

The accessory protein negative factor (Nef) from human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) is required for optimal viral infectivity and the progression to acquired immunodeficiency syndrome (AIDS). Nef interacts with the endocytic machinery, resulting in the down-regulation of cluster of differentiation antigen 4 (CD4) and major histocompatibility complex class I (MHCI) molecules on the surface of infected cells. Mutations in the C-terminal flexible loop of Nef result in a lower rate of internalization by this viral protein. However, no loop-dependent binding of Nef to adaptor protein-2 (AP-2), which is the adaptor protein complex that is required for the internalization of proteins from the plasma membrane, could be demonstrated. In this study we investigated the relevance of different motifs in Nef from SIVmac239 for its internalization, CD4 down-regulation, binding to components of the trafficking machinery, and viral infectivity. Our data suggest that the binding of Nef to the catalytic subunit H of the vacuolar membrane ATPase (V-ATPase) facilitates its internalization. This binding depends on the integrity of the whole flexible loop. Subsequent studies on Nef mutant viruses revealed that the flexible loop is essential for optimal viral infectivity. Therefore, our data demonstrate how Nef contacts the endocytic machinery in the absence of its direct binding to AP-2 and suggest an important role for subunit H of the V-ATPase in viral infectivity.

Essential role for mammalian copper transporter Ctr1 in copper homeostasis and embryonic development

The trace metal copper (Cu) plays an essential role in biology as a cofactor for many enzymes that include Cu, Zn superoxide dismutase, cytochrome oxidase, ceruloplasmin, lysyl oxidase, and dopamine β-hydroxylase. Consequently, Cu transport at the cell surface and the delivery of Cu to intracellular compartments are critical events for a wide variety of biological processes. The components that orchestrate intracellular Cu trafficking and their roles in Cu homeostasis have been elucidated by the studies of model microorganisms and by the characterizations of molecular basis of Cu-related genetic diseases, including Menkes disease and Wilson disease. However, little is known about the mechanisms for Cu uptake at the plasma membrane and the consequences of defects in this process in mammals. Here, we show that the mouse Ctr1 gene encodes a component of the Cu transport machinery and that mice heterozygous for Ctr1 exhibit tissue-specific defects in copper accumulation and in the activities of copper-dependent enzymes. Mice completely deficient for Ctr1 exhibit profound growth and developmental defects and die in utero in mid-gestation. These results demonstrate a crucial role for Cu acquisition through the Ctr1 transporter for mammalian Cu homeostasis and embryonic development.

Transcription factor TFIIH and DNA endonuclease Rad2 constitute yeast nucleotide excision repair factor 3: implications for nucleotide excision repair and Cockayne syndrome.

Nucleotide excision repair (NER) of ultraviolet light-damaged DNA in eukaryotes requires a large number of highly conserved protein factors. Recent studies in yeast have suggested that NER involves the action of distinct protein subassemblies at the damage site rather than the placement there of a "preformed repairosome" containing all the essential NER factors. Neither of the two endonucleases, Rad1-Rad10 and Rad2, required for dual incision, shows any affinity for ultraviolet-damaged DNA. Rad1-Rad10 forms a ternary complex with the DNA damage recognition protein Rad14, providing a means for targeting this nuclease to the damage site. It has remained unclear how the Rad2 nuclease is targeted to the DNA damage site and why mutations in the human RAD2 counterpart, XPG, result in Cockayne syndrome. Here we examine whether Rad2 is part of a higher order subassembly. Interestingly, we find copurification of Rad2 protein with TFIIH, such that TFIIH purified from a strain that overexpresses Rad2 contains a stoichiometric amount of Rad2. By several independent criteria, we establish that Rad2 is tightly associated with TFIIH, exhibiting an apparent dissociation constant < 3.3 x 10(-9) M. These results identify a novel subassembly consisting of TFIIH and Rad2, which we have designated as nucleotide excision repair factor 3. Association with TFIIH provides a means of targeting Rad2 to the damage site, where its endonuclease activity would mediate the 3' incision. Our findings are important for understanding the manner of assembly of the NER machinery and they have implications for Cockayne syndrome.

Financial bills and receipts, 1781

One-page account between William and Joseph Croswell for board and supplies.

Copy of William Watson's account for painting and glazing of Holden Chapel, September 1801

Contains an itemized list of costs for painting and glazing tasks to be completed and supplies needed by Watson for Holden Chapel. Tasks include painting Doctor Warren's room twice, painting window sashes and shutters, transporting glass from Boston, and setting each window pane. Supplies needed include oil, white lead, and putty.

Instructions for printing the Hebrew Grammar, [ca. 1735]

A one-page handwritten list of instructions, in President Benjamin Wadsworth's hand, for printing, distributing, and collecting revenue on the Hebrew Grammar.

Commonplace book of Hector Orr, 1789-1804

Hector Orr began recording entries in this commonplace book during his first year as a student at Harvard and continued writing in the volume sporadically until 1804. The entries written while he was a student, from 1789 to 1792, include themes written on the following topics: Time, Discontent, Patriotism, Virtue, Conscience, Patience, Avarice, Compassion, Mortality, Self-knowledge, Benevolence, Morning, Anger, Profanity, Bribery, Autumn and Winter, Hermitage, Conscience and Anticipation. He also wrote detailed entries about the forensic disputations in which he and his classmates participated, explaining both the affirmative and negative positions. One of these disputations involved discussion of the Stamp Act, which was then quite recent history. Orr's entries about the disputations list the names of students involved and specify their position in the argument.

Maryland and Delaware, 1797 Raster Image

This layer is a digitized geo-referenced raster image of a 1797 map of Maryland and Delaware drawn by D.F. Sotzmann. These Sotzmann maps (10 maps of New England and Mid-Atlantic states) typically portray both natural and manmade features. They are highly detailed with symbols for churches, roads, court houses, distilleries, iron works, mills, academies, county lines, town lines, and more. Relief is usually indicated by hachures and country boundaries have also been drawn. Place names are shown in both German and English and each map usually includes an index to land grants. Prime meridians used for this series are Greenwich and Washington, D.C.

The Market for Tractors in the EU: Price Differences and Convergence. Factor Markets Working Documents No. 35, February 2013

This study evaluates the degree of segmentation of the market for agricultural machinery and equipment in the EU. We focus on agricultural tractors, the most common and biggest investment in machinery and equipment in the agricultural sector. By using country price data for individual tractor models, we test the law of one price, i.e. the existence of a common price for tractors across EU member states. We find that significant price differences exist, yet unlike most other studies we find that large price deviations are penalised within a short time. The study also shows that transport costs are an important source of price differences, as domestic production leads to lower prices on the domestic market and as price convergence is negatively correlated with distance. Finally, price differences should not solely be understood from a geographical perspective, as evidence supports the idea that farmers’ buying power is significant in explaining price differences within countries.

Investment behaviour of EU arable crop farms in selected EU countries and the impact of policy reforms. Factor Markets Working Document No. 42, May 2013

This deliverable provides a comparative analysis, among selected EU member states, of the investment demand of a sample of specialised field crop farms for farm buildings, machinery and equipment as determined by different types and levels of Common Agricultural Policy support. It allows for the existence of uncertainty in the price of output farmers receive and for both long- and short-run determinants of investment levels, as well as for the presence of irregularities in the cost adjustment function due to the existence of threshold-type behaviours. The empirical estimation reveals that three investment regimes are consistently identified in Germany and Hungary, across asset and support types, and in France for machinery and equipment. More traditional disinvestment-investment type behaviours characterise investment in farm building in France and the UK, across support types, and Italy for both asset classes under coupled payments. The long-run dynamic adjustment of capital stocks is consistently and significantly estimated to be towards a – mostly non-stationary – lower level of capitalisation of the farm analysed. By contrast, the expected largely positive short-run effects of an increase in output prices are often not significant. The effect of CAP support on both types of investment is positive, although seldom significant, while the proxy for uncertainty employed fails to be significant yet, in most cases, has the expected effect of reducing the investment levels.

The China-Russia trade relationship and its impact on Europe. Breugel Working Paper Issue 4, 2016

This paper analyses empirically how increasingly close trade relations between China and Russia might affect the European Union (EU). We show that EU countries are complementary to Russia on the Chinese market. However, Chinese exports are increasingly relevant substitutes for EU exports on the Russian market. This means that an increase in China-Russia economic cooperation should have a negative impact on European exports. We simulate a scenario in which trade tariffs between Russia and China are eliminated, which is found to reduce EU exports to Russia. Finally, a more granular approach to the question analyses which sectors in Europe will be more affected by the increasing economic links between China and Russia, and finds that electronic machinery, equipment and machinery, and nuclear reactors will be particularly affected. Such findings obviously show quickly China is moving up the ladder in terms of export structure and how strategically important it is for Europe to continue upgrading its industry to compete at the highest level of that ladder.

Hyperosmotic stress memory in Arabidopsis is mediated by distinct epigenetically labile sites in the genome and is restricted in the male germline by DNA glycosylase activity

Inducible epigenetic changes in eukaryotes are believed to enable rapid adaptation to environmental fluctuations. We have found distinct regions of the Arabidopsis genome that are susceptible to DNA (de)methylation in response to hyperosmotic stress. The stress-induced epigenetic changes are associated with conditionally heritable adaptive phenotypic stress responses. However, these stress responses are primarily transmitted to the next generation through the female lineage due to widespread DNA glycosylase activity in the male germline, and extensively reset in the absence of stress. Using the CNI1/ATL31 locus as an example, we demonstrate that epigenetically targeted sequences function as distantly-acting control elements of antisense long non-coding RNAs, which in turn regulate targeted gene expression in response to stress. Collectively, our findings reveal that plants use a highly dynamic maternal 'short-term stress memory' with which to respond to adverse external conditions. This transient memory relies on the DNA methylation machinery and associated transcriptional changes to extend the phenotypic plasticity accessible to the immediate offspring.

The care of books : an essay on the development of libraries and their fittings, from the earliest times to the end of the eighteenth century /

Includes bibliographical references.