Elucidation of the Functional Architecture of the Early Pre-Ribosomal Processing Machinery in Yeast

Ribosomes carry out one of the most fundamental functions of life - the translation of genetic information into functional proteins. The pivotal role of the ribosome in the cell is reflected in its immensely complicated and energy-consuming assembly pathway. The maturation of a eukaryotic ribosome involves more than 200 non-ribosomal factors and the activity of all three RNA polymerases. In yeast, ribosome biogenesis starts with the transcription of the 35S pre-ribosomal RNA in the nucleolus. This large RNA molecule contains three of the four ribosomal RNAs separated by several internal and external transcribed spacer regions. The 5’ external transcribed spacer (5’ETS) is the first RNA domain of the 35S pre-rRNA being transcribed. As it emerges from the RNA polymerase it is bound by UtpA, a 660 kDa complex consisting of 7 essential subunits in yeast. 9 By binding to the nascent pre-rRNA, UtpA triggers the association of multiple other proteins and complexes, which leads to the formation of the ~2 MDa 5’ ETS particle. As transcription continues through the ensuing small subunit rRNA gene more ribosome biogenesis factors as well as ribosomal proteins are recruited and the 5’ ETS particle evolves into the small subunit processome. The small subunit processome, a giant particle, unique and essential to eukaryotes, coordinates the cleavage of the 35S pre-rRNA to separate the maturation of the small and large ribosomal subunit. So far, a functional understanding of the initial events in ribosome biogenesis has been impeded by a lack of structural and biochemical data about the protein complexes facilitating this process and the pre-ribosomal particles they form. To gain mechanistic insights into these earliest steps we set out to delineate the role of UtpA as first building block, vital structural component and organizer of the 5’ ETS particle and the small subunit processome. By using protein-protein and RNA-protein cross-linking techniques combined with negative stain electron microscopy and biochemical assays we were able to define the composite RNA binding site of UtpA and characterize its molecular architecture in the absence of high-resolution structural data (Chapter II). Subsequent structure determination of the small subunit processome by cryoelectron microscopy has not only provided the first fully assigned atomic model of UtpA but visualized how ribosome biogenesis factors keep the ribosomal RNA domains in spatially separated compartments of this large particle (Chapter III). In the small subunit processome, the 5’ ETS particle forms the base onto which the segregated ribosomal RNA domains are folded. To investigate whether the 5’ ETS particle serves as a structural mold for the maturing rRNA domains during earlier assembly stages, we solved the cryo-EM structures of the 5’ ETS particle in intermediates preceding the formation of the small subunit processome (Chapter IV). Combined with the in vivo analysis of artificial pre-rRNA fragments, the architecture of the 5’ ETS particle shows that the initial steps of ribosome assembly are governed by the functional independence of all rRNA domains and the 5’ ETS particle. Completion of ribosomal gene transcription then leads to a conformational change in the 5’ ETS particle and small subunit processome formation. In summary, our work provides structural snapshots and biochemical information on more than 50 ribosome assembly factors during different stages of the initiating steps in eukaryotic ribosome biogenesis. These data form the basis for a three-dimensional model of these essential events in the eukaryotic cell

Regulators of male and female sexual development are critical for the transmission of a malaria parasite

Malaria transmission to mosquitoes requires a developmental switch in asexually dividing blood-stage parasites to sexual reproduction. In Plasmodium berghei, the transcription factor AP2-G is required and sufficient for this switch, but how a particular sex is determined in a haploid parasite remains unknown. Using a global screen of barcoded mutants, we here identify genes essential for the formation of either male or female sexual forms and validate their importance for transmission. High-resolution single-cell transcriptomics of ten mutant parasites portrays the developmental bifurcation and reveals a regulatory cascade of putative gene functions in the determination and subsequent differentiation of each sex. A male-determining gene with a LOTUS/OST-HTH domain as well as the protein interactors of a female-determining zinc-finger protein indicate that germ-granule-like ribonucleoprotein complexes complement transcriptional processes in the regulation of both male and female development of a malaria parasite

ERM Report 2020: Die Rolle der Risk Manager in der COVID-19 Krise

Kein Abstract vorhanden+ ID der Publikation: hslu_81206 + Art des Beitrages: Studie oder Gutachten + Sprache: Deutsch + Letzte Aktualisierung: 2020-12-17 14:43:5

[Transcatheter Treatment of Severe Tricuspid Regurgitation].

Transcatheter Treatment of Severe Tricuspid Regurgitation Abstract. Severe tricuspid regurgitation can lead to increased morbidity and mortality due to clinical symptoms and impairment of organ function. With the emergence of new interventional treatment options, the once neglected tricuspid valve is receiving increased attention. The following article intends to provide an overview of the causes, diagnostic modalities, and therapeutic options of severe tricuspid regurgitation

Levosimendan as Treatment Option in Severe Verapamil Intoxication: A Case Report and Review of the Literature

Copyright © 2010 Mirjam Osthoff et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Cardiovascular shock due to verapamil intoxication is often refractory to standard resuscitation methods. Recommended therapy includes prevention of further absorption of the drug, inotropic therapy, calcium gluconate, and hyperinsulinemia/euglycemia therapy. Often further measures are needed such as ventricular pacing or mechanical circulatory support. Still, mortality remains high. Levosimendan, an inotropic agent, that enhances myofilament response to calcium, increases myocardial contraction and could therefore be beneficial in verapamil intoxication. Here, we report the case of a 60-year-old patient with clinically severe verapamil poisoning who presented with shock, bradycardia, and sopor. Standard therapy including high-dose inotropes failed to ameliorate the signs of intoxication. But additional therapy with levosimendan led to rapid improvement. Based on this observation, the literature is reviewed focusing on utilization of levosimendan in the treatment of calcium channel blocker overdose. We suggest to consider levosimendan as additional treatment option in patients with cardiovascular shock due to verapamil intoxication that are refractory to standard management. 1

Procalcitonin for guidance of antibiotic therapy

Procalcitonin is a surrogate biomarker for estimating the likelihood of a bacterial infection. Procalcitonin-guided initiation and termination of antibiotic therapy is a novel approach utilized to reduce antibiotic overuse. This is essential to decrease the risk of side effects and emerging bacterial multiresistance. Interpretation of procalcitonin levels must always comprise the clinical setting and knowledge about assay characteristics. Only highly sensitive procalcitonin assays should be used in clinical practice and cut-off ranges must be adapted to the disease and setting. Highly sensitive procalcitonin measurements, embedded in diagnosis-specific clinical algorithms, have been shown to markedly reduce the overuse of antibiotic therapy without increasing risk to patients in 11 randomized controlled trials including over 3500 patients from different European countries. In primary care and emergency department patients with mild and mostly viral respiratory infections (acute bronchitis), the initial prescription of antibiotics was reduced by 30-80%. In hospitalized and more severely ill patients with community-acquired pneumonia and sepsis, the main effect was a reduction of the duration of antibiotic courses by 25-65%. This review aims to provide physicians with an overview of the strengths and limitations of procalcitonin guidance for antibiotic therapy when used in different clinical settings and in patients with different underlying infections