Full-length prepro-alpha-factor can be translocated across the mammalian microsomal membrane only if translation has not terminated.

We have previously shown that fully synthesized prepro-alpha-factor (pp alpha F), the precursor for the yeast pheromone alpha-factor, can be translocated posttranslationally across yeast rough microsomal (RM) membranes from a soluble, ribosome-free pool. We show here that this is not the case for translocation of pp alpha F across mammalian RM. Rather we found that a small amount of translocation of full-length pp alpha F is observed, but is solely due to polypeptide chains that were still ribosome bound and covalently attached to tRNA, i.e., not terminated. In addition, both signal recognition particle (SRP) and SRP receptor are required, i.e., the same targeting machinery that is normally responsible for the coupling between protein synthesis and translocation. Thus, the molecular requirements for targeting are distinct from posttranslational translocation across yeast RM. As termination is generally regarded as part of translation, the translocation of full-length pp alpha F across mammalian RM does not occur "posttranslationally," albeit independent of elongation. Most other proteins for which posttranslational translocation across mammalian RM was previously claimed fall into the same category in that ribosome attachment as peptidyl-tRNA is required. To clearly separate these two distinct processes, we suggest that the term posttranslational be reserved for those processes that occur in the complete absence of the translational machinery. We propose the term "ribosome-coupled translocation" for the events described here

The dynamics of research networks in Brite-Euram

Network formation within the BRITE-EURAM program is investigated. We describe the role of the hub of the network, which is defined as the set of main contractors that account for most of the participations. We study the effects that the conflict of objectives within European research funding between precompetitive research vs. European cohesion has on the formation of networks and on the relationship between different partners of the network. A panel data set is constructed including the second and third framework of the Brite–Euram program. A model of joint production of research results is used to test for changes in the behavior of partners within the two frameworks. The main findings are that participations are very concentrated, that is a small group of institutions account for most of the participations, but going from the second to the third framework the presence of subcontractors and single participants increases substantially. This result is reinforced by the fact that main contractors receive smaller spill-ins within networks, but spill-ins increase from the second to the third framework.mathematical economics and econometrics ;

The quality of the Catalan and Spanish education systems: A perspective from PISA

For Catalonia and Spain, public perception is that the PISA reports show that their education systems are underperforming. The goal of this chapter is to quantify how much of the Catalan and Spanish PISA score can be attributed to the education levels of parents and what part must instead be explained by other factors. To do so we use standard statistical techniques to examine how the Catalan and Spanish PISA score would have compared with other countries and regions if all had the same parental education levels and immigration levels. For Spain the main results show that there is a sizable increase in PISA scores relative to the rest of Europe when parental schooling is accounted for. But Spain's performance is rather poor to start out with and only rises to somewhat above average when accounting for parental education levels. For Catalonia accounting for parental education levels leads to small improvements in the PISA score compared to other Spanish regions and to Flanders, Lombardy, and Denmark. Moreover, immigration or the concentration of immigrants at some schools accounts for little of the below average performance of Catalonia.Catalan education systems; Spanish education systems;

European research funding and regional technological capabilities: Network composition analysis

We use network and correspondence analysis to describe the composition of the research networks in the European BRITE--EURAM program. Our main finding is that 27\% of the participants in this program fall into one of two sets of highly ``interconnected'' institutions --one centered around large firms (with smaller firms and research centers providing specialized services), and the other around universities--. Moreover, these ``hubs'' are composed largely of institutions coming from the technologically most advanced regions of Europe. This is suggestive of the difficulties of attaining European ``cohesion'', as technically advanced institutions naturally link with partners of similar technological capabilities.Management of technological innovation and R&D,government policy

Targeting of the hepatitis B virus precore protein to the endoplasmic reticulum membrane: after signal peptide cleavage translocation can be aborted and the product released into the cytoplasm.

The major hepatitis B virus (HBV) core protein is a viral structural protein involved in nucleic acid binding. Its coding sequence contains an extension of 29 codons (the "precore" region) at the amino terminus of the protein which is present in a fraction of the viral transcripts. This region is evolutionarily conserved among mammalian and avian HBVs, suggesting it has functional importance, although at least for duck HBV it has been shown to be nonessential for replication of infectious virions. Using in vitro assays for protein translocation across the endoplasmic reticulum membrane, we found that the precore region of the HBV genome encodes a signal sequence. This signal sequence was recognized by signal recognition particle, which targeted the nascent precore protein to the endoplasmic reticulum membrane with efficiencies comparable to those of other mammalian secretory proteins. A 19-amino acid signal peptide was removed by signal peptidase on the lumenal side of the microsomal membrane, generating a protein similar to the HBV major core protein, but containing 10 additional amino acids from the precore region at its amino terminus. Surprisingly, we found that 70-80% of this signal peptidase-cleaved product was localized on the cytoplasmic side of the microsomal vesicles and was not associated with the membranes. We conclude that translocation was aborted by an unknown mechanism, then the protein disengaged from the translocation machinery and was released back into the cytoplasm. Thus, a cytoplasmically disposed protein was created whose amino terminus resulted from signal peptidase cleavage. The remaining 20-30% appeared to be completely translocated into the lumen of the microsomes. A deletion mutant lacking the carboxy-terminal nucleic acid binding domain of the precore protein was similarly partitioned between the lumen of the microsomes and the cytoplasmic compartment, indicating that this highly charged domain is not responsible for the aborted translocation. We discuss the implications of our findings for the protein translocation process and suggest a possible role in the virus life cycle

Trade liberalization in Uruguay: Domestic and foreign firms

The reallocation of resources is one of the main impacts of trade liberalization processes. In the case of manufacturing industries resources will be reallocated from import--competing sectors to export--oriented sectors. This paper studies the effects that a more open economic environment has had on the entry conditions for foreign and domestic firms in Uruguayan manufacturing industries. We find significant differences in the behavior of foreign and domestic firms, both when they are incumbents or when they act as potential entrants. In general, foreign firms seem to be more successful in applying entry deterring strategies, due to advantages in foreign markets, deeper financial resources or better technological capabilities. They also appear to be more responsive to entry conditions when they face the prospects of entering a given industry.Production and market structure,industry studies

Sobre uma cena de "Fim de semana no Parque", do Racionais MC's

The article analyses some musical and poetical techniques of the rap "Fim de semana no Parque" (1993) and means to study some critical aspects made by Racionais MC's about the life in São Paulo city and in Brazil.O artigo analisa alguns recursos musicais e poéticos do rap "Fim de semana no Parque" (1993) e busca interpretar aspectos da crítica feita pelos Racionais MC's à vida na cidade de São Paulo e no Brasil

Continuity properties of a factor of Markov chains

Starting from a Markov chain with a finite alphabet, we consider the chain obtained when all but one symbol are undistinguishable for the practitioner. We study necessary and sufficient conditions for this chain to have continuous transition probabilities with respect to the past

Balance Sheet Effects in Currency Crises: Evidence from Brazil

In third generation currency crises models, balance sheet losses from currency depreciations propagate the crises into the real sector of the economy. To test these models, we built a firmlevel database that allowed us to measure currency mismatches around the 2002 Brazilian currency crisis. We found that between 2001 and 2003, firms with large currency mismatches just before the crisis reduced their investment rates 8.1 percentage points more than other publicly held firms. We also showed that the currency depreciation increased exporters revenue, but those with currency mismatches reduced investments 12.5 percentage points more than other exporters. These estimated reductions in investment are economically very significant, underscoring the importance of negative balance sheet effects in currency crises. Jel Codes:F32; F34; G31; G32Investment; Balance sheets; Currency crises; Hedge; Financial constraints.