Structural analysis of stalled ribosomal complexes and their respective rescue mechanisms by Cryo-Electron Microscopy

The ribosome is a multifunctional ribonucleoprotein complex responsible for the translation of the genetic code into proteins. It consists of two subunits, the small ribosomal subunit and the large ribosomal subunit. During initiation of translation, both subunits join and form a functional 70S ribosome that is capable of protein synthesis. In the course of elongation, the ribosome synthesizes proteins according to the codons on the mRNA until it encounters a stop codon leading to the recruitment of release factors 1 or 2 followed by release of the nascent chain. Upon release of the polypeptide chain the subunits dissociate from each other and can be recruited for another round of translation. There are two scenarios that interfere with active translation, namely the formation of so called ‘non-stop’ or ‘no-go’ complexes. In both cases, ribosomes pause translation and without interference of additional factors, they would become stalled. Accumulation of such events leads to a decrease of ribosomal subunits that can be recruited for translation, ultimately resulting in the death of the cell. Using cryo-electron microscopy (cryo-EM), we obtained the structure of alternative rescue factor A (ArfA) together with release factor 2 bound to a ‘non-stop’ complex. Our reconstructions showed that the C-terminal domain of ArfA occupies the empty mRNA channel on the SSU, whereas the N-terminal domain provides a platform for recruiting RF2 in a stop codon-independent way. Thereby, ArfA stabilizes a unique conformation of the switch loop of RF2, responsible for directing the catalytically important GGQ motif towards the PTC. The high-resolution structure of ArfA allowed us to compare its mode of action with trans-translation and alternative rescue factor B, two other factors operating on ‘non-stop’ complexes. A second project focused on elongation factor P (EF-P), a factor that alleviates stalling on polyproline stalled ribosomes. Applying cryo-EM, we were able to show that in the absence of EF-P, the nascent chain is destabilized as the polyproline moiety attached to the P-tRNA is not able to accommodate within the ribosomal tunnel. Binding of modified EF-P to the polyproline stalled complex stabilizes the P-site tRNA and especially the CCA, thereby forcing the nascent chain to adopt an alternative conformation that is favorable for translation to proceed

Dinámicas socio-económicas del agro pampeano actual y espacios locales: una propuesta de análisis

En las últimas décadas se han producido transformaciones en el agro queplantean desafíos para pensar las dinámicas actuales que lo atraviesan;entre otras cosas, en relación al modelo productivo que se ha conformado,a los procesos por los que han atravesado los diversos agentes directamentevinculados a la actividad, a las dinámicas socio-económicas que se desplieganvinculadas al agro y a su impacto en los espacios locales. En estetrabajo se reflexiona sobre lo ocurrido en el agro argentino, más particularmentepampeano, en relación a tales problemáticas. Se comenzará porconsiderar algunos procesos de cambio ocurridos en el agro a nivel global;para analizar luego las tendencias dominantes del agro pampeano, quepermiten afirmar la conformación de un nuevo modelo de desarrollo agrario.Luego, tomando en cuenta diversos antecedentes, se realiza una propuestaconceptual para abordar el problema de las dinámicas territorialesde los actores agrarios en sus aspectos económicos y su incidencia en losespacios locales. Dinámica que no ha sido estudiada específicamente desdeesta perspectiva que pone énfasis en los elementos económico-productivos implicados en las construcciones, deconstrucciones y reconstrucciones delos territorios, apelando para ello a la noción de circulación del capital delos actores agrarios; y que resulta un punto relevante para comprender losprocesos que se despliegan hoy en el desarrollo agrario.In the last decades, transformations in the rural sector set out challenges to think the current dynamics that underlies it; among other things, related to the production model that has been defined, to the processes that different stakeholders directly related to the activity have gone through, and to the socio-economic dynamics linked to the rural sector that unfold and their impact on local spaces. This paper reflects on what has happened in rural Argentina, particularly in the Pampas Region, in relation to these problems. The paper starts by considering some transformation processes that have taken place in the rural sector at a global level to analyse, then, the dominant trends of the rural sector in the Pampas region that allow us to affirm that a new model of agricultural development has been introduced. On the basis of various antecedents, the paper will then present a conceptual proposal to address the problem of the territorial dynamics of the rural actors, the economic aspects and their incidence on local spaces. This dynamics has not been studied specifically from this perspective, and emphasizes the economic-productive elements implied in the constructions, deconstructions and reconstructions of territories, resorting to the notion of capital circulation of the rural actors which constitutes a relevant point to understand the processes that emerge today in agricultural development.Fil: Huter, Estefanía. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Centro de Investigaciones sobre Economía y Sociedad en la Argentina Contemporánea; Argentin

Die Pastoralinstruktion "Cornmunio et Progressio" und das neue christliche Bild vom Menschen

„ ... Was an der Haltung der Kirchen auffällt, ist ihre heraushängende Zunge.Atemlos jappend laufen sie hinter der Zeit her, auf daß ihnen niemand entwische .... Diese Kirchen schaffen nichts, sie wandeln das von anderen Geschaffene, das von anderen Entwickelte in Elemente um, die ihnen nutzbar sein könnten .... "Diese bissige Bemerkung Kurt Tucholskys1 fällt einem unwillkürlich ein, wenn  an sich mit der Pastoralinstruktion „Communio et Progressio" kritisch auseinandersetzt. (...) English The Vatican Council Decree "Inter Mirifica", which Fr. Mole has consistently defended, asked for a Pastoral Instruction. This latter document, however, when issued, „discredits the vety same Council document published by the same Pope" in Fr. Mole's opinion. He takes this as his starting point for a weil thought out comparison between the two documents. The method used in composing a document like the Pastoral Instruction, that is, Collegiality through co-operators from all over the world, is still in its early stages. On the other hand, documents on the Social Teaching of the Church, elaborated by members of the Roman Curia, are, in his opinion, much better. The author reproaches the lnstruction with lacking in clarity and in underestimating the ethical aspects of communication.

Structural analysis of stalled ribosomal complexes and their respective rescue mechanisms by Cryo-Electron Microscopy

The ribosome is a multifunctional ribonucleoprotein complex responsible for the translation of the genetic code into proteins. It consists of two subunits, the small ribosomal subunit and the large ribosomal subunit. During initiation of translation, both subunits join and form a functional 70S ribosome that is capable of protein synthesis. In the course of elongation, the ribosome synthesizes proteins according to the codons on the mRNA until it encounters a stop codon leading to the recruitment of release factors 1 or 2 followed by release of the nascent chain. Upon release of the polypeptide chain the subunits dissociate from each other and can be recruited for another round of translation. There are two scenarios that interfere with active translation, namely the formation of so called ‘non-stop’ or ‘no-go’ complexes. In both cases, ribosomes pause translation and without interference of additional factors, they would become stalled. Accumulation of such events leads to a decrease of ribosomal subunits that can be recruited for translation, ultimately resulting in the death of the cell. Using cryo-electron microscopy (cryo-EM), we obtained the structure of alternative rescue factor A (ArfA) together with release factor 2 bound to a ‘non-stop’ complex. Our reconstructions showed that the C-terminal domain of ArfA occupies the empty mRNA channel on the SSU, whereas the N-terminal domain provides a platform for recruiting RF2 in a stop codon-independent way. Thereby, ArfA stabilizes a unique conformation of the switch loop of RF2, responsible for directing the catalytically important GGQ motif towards the PTC. The high-resolution structure of ArfA allowed us to compare its mode of action with trans-translation and alternative rescue factor B, two other factors operating on ‘non-stop’ complexes. A second project focused on elongation factor P (EF-P), a factor that alleviates stalling on polyproline stalled ribosomes. Applying cryo-EM, we were able to show that in the absence of EF-P, the nascent chain is destabilized as the polyproline moiety attached to the P-tRNA is not able to accommodate within the ribosomal tunnel. Binding of modified EF-P to the polyproline stalled complex stabilizes the P-site tRNA and especially the CCA, thereby forcing the nascent chain to adopt an alternative conformation that is favorable for translation to proceed

Tehnologija uzgoja dagnji (mytilus galloprovincialis) i kamenica (ostrea edulis) u Bokokotorskom zalivu

Razvoj marikulture u Crnoj Gori je jedno od strateški važnih pitanja u programima proizvodnje hrane za domaće tržište i za izvoz. Program podrazumijeva proizvodnju, odnosno uzgoj nekoliko vrsta školjaka i riba, dok je u planu i uzgoj rakova. Marikultura je sve značajnija privredna grana u svijetu jer nadoknađuje smanjene potencijale hrane iz prirodnih izvora. I pored naglašenog značaja marikulture, izuzetnih bioloških i ekoloških karakteristika priobalnog mora Crne Gore, naučnog-stručnog znanja, moramo konstatotovati da je uzgoj morskih organizama na navedenom području tek u inicijalnom začetku, čak i kada se radi o uzgoju školjaka, čija je sadašnja proizvodnja oko 200 t. godišnje, što ostvaruje 16 uzgajivača u Bokokotorskom zalivu- uglavnom u Kotorskom i Tivatskom dijelu. Dakle, cijela marikultura u Crnoj Gori koncentrisana je na područje Bokokotorskog zaliva, dok je otvoreno more, u tom smislu, ostalo potpuno neiskorišćeno. U davna vremena način uzgoja školjaka bio je vrlo jednostavan. Grane hrasta, trešnje, masline i ostalog raspoloživog materijala su se sakupljale i bacale u more. Na tako bačene grane hvatala se mlađ školjaka (kamenica i dagnji), a nakon tri godine i nekoliko faza uzgoja proces je bio kompletan, školjke su se vadile iz mora, te otpremale na tržište. Cilj ovog rada je da damo svojevrsni pregled, počevši od prvih istraživanja mogućnosti uzgoja dagnji i kamenica u Bokokotorskom zalivu do današnjeg stanja i pravaca u kojima bi marikultura trebala da se razvoja u Crnoj Gori

Excision of damaged bases from transcription intermediates by FPG/NEI superfamily DNA glycosylases

Oxidative lesions are abundant due to constant presence of reactive oxygen species in living cells. Repair of oxidative base lesions is initiated by DNA glycosylases. For example, bacterial Fpg and Nei DNA glycosylases excise oxidized purines and pyrimidines, respectively, from DNA. Their human homologs, NEIL1 and NEIL2, have been reported to show preference towards oxidized lesions in DNA bubbles. From these observations, it had been hypothesized that NEIL proteins may be involved in the repair of lesions in DNA bubbles generated during transcription. However, it is not presently clear how NEILs would behave on bubbles more closely resembling transcription intermediates (e. g., containing the RNA strand), and bacterial homologs Fpg and Nei had never been investigated with bubble substrates. We have studied excision of either 8-oxoguanine (8-oxoG) or 5,6-dihydrouracil (DHU) by E. coli Fpg and Nei and human NEIL1 and NEIL2 from single-strand oligonucleotides, perfect duplexes, bubbles with different number of unpaired bases (6 to 30), Dloops with DNA or RNA and from complexes with RNA polymerase. Fpg, NEIL1 and NEIL2 efficiently excised DHU located inside a bubble. Fpg and NEIL1 was generally more active than NEIL2 in excision of 8-oxoG from ssDNA and bubbles. Nei, on the other hand, was active only on DHU located in dsDNA (either perfect duplex or DNA/DNA D-loop). Fpg and NEIL1 also have shown activity in D-loops with RNA. The activity of Fpg was observed in pre-assembled transcriptional complexes with E. coli RNA polymerase and depended on the position of the lesion in the transcription bubble, possibly reflecting local accessibility of the lesion within the elongation complex

Alois Vojtěch Šembera, Lehrer für böhmische Sprache und Literatur an der Universität Wien

In meiner Diplomarbeit beschäftige ich mich mit Alois Vojtěch Šembera (1807, Vysoké Mýto - 1882, Wien), der als Jurist, Philologe, Literaturwissenschaftler, Historiker und Ethnograph in Brünn (Brno), Olmütz (Olomouc) und Wien wirkte. Weil sein Rang als Lehrer und Wissenschaftler unterschiedlich beurteilt wird, war Ziel der Arbeit, seine Tätigkeit an der Universität Wien genauer zu untersuchen. Dort lebte und arbeitete er mehr als 30 Jahre lang und hatte ab dem Jahr 1849 die Stelle eines Lehrers für böhmische Sprache und Literatur an der Universität Wien inne. Der Mangel an deutschsprachiger Literatur über Šembera beziehungsweise seine Aussparung aus Werken zur Wiener Bohemistik und Slawistik waren ein besonderer Anreiz für die Bearbeitung dieses Themas. Es werden zunächst die Geschichte der Universität Wien, jene der Wiener Slawistik und Bohemistik beleuchtet, wobei Šemberas Vorgänger als Lehrer der böhmischen Sprache an der Universität berücksichtigt werden. Anschließend stellt eine Biographie die wichtigsten Stationen in Šemberas Leben dar. Ein Überblick über sein Werk zeigt sein Schaffen in verschiedenen Wissenschaftsdisziplinen. Die Edition und Analyse von bisher unveröffentlichten Dokumenten aus dem österreichischen Staatsarchiv und dem Archiv der Universität Wien, die seinen erfolglosen Kampf um eine Professur belegen, bieten einen Gegensatz zur verherrlichenden Betrachtung seines Wirkens an der Universität Wien in der Literatur

Visualization of translation termination intermediates trapped by the Apidaecin 137 peptide during RF3-mediated recycling of RF1.

During translation termination in bacteria, the release factors RF1 and RF2 are recycled from the ribosome by RF3. While high-resolution structures of the individual termination factors on the ribosome exist, direct structural insight into how RF3 mediates dissociation of the decoding RFs has been lacking. Here we have used the Apidaecin 137 peptide to trap RF1 together with RF3 on the ribosome and visualize an ensemble of termination intermediates using cryo-electron microscopy. Binding of RF3 to the ribosome induces small subunit (SSU) rotation and swivelling of the head, yielding intermediate states with shifted P-site tRNAs and RF1 conformations. RF3 does not directly eject RF1 from the ribosome, but rather induces full rotation of the SSU that indirectly dislodges RF1 from its binding site. SSU rotation is coupled to the accommodation of the GTPase domain of RF3 on the large subunit (LSU), thereby promoting GTP hydrolysis and dissociation of RF3 from the ribosome