tRNA-derived fragments target the small ribosomal subunit to fine-tune translation

Post-transcriptional cleavage of RNA molecules to generate smaller fragments is a widespread mechanism that enlarges the structural and functional complexity of cellular RNomes. In particular, fragments deriving from both precursor and mature tRNAs represent one of the rapidly growing classes of post-transcriptional RNA pieces. Importantly, these tRNA-derived fragments (tRFs) possess distinct expression patterns, abundance, cellular localizations, or biological roles compared with their parental tRNA molecules [1]. Here we present evidence that tRFs from the archaeon Haloferax volcanii directly bind to ribosomes. In a previous genomic screen for ribosome-associated small RNAs we have identified a 26 residue long fragment originating from the 5’ part of valine tRNA (Val-tRF) to be by far the most abundant tRF in H. volcanii [2]. The Val-tRF is processed in a stress- dependent manner and was found to primarily target the small ribosomal subunit in vitro and in vivo. Translational activity was markedly reduced in the presence of Val-tRF, while control RNA fragments of similar length did not show inhibition of protein biosynthesis. Crosslinking experiments and subsequent primer extension analyses revealed the Val-tRF interaction site to surround the mRNA path in the 30S subunit. In support of this, binding experiments demonstrated that Val-tRF does compete with mRNAs for ribosome binding. Therefore this tRF represents a ribosome-bound non-protein-coding RNA (ncRNA) capable of regulating gene expression in H. volcanii under environmental stress conditions probably by fine-tuning the rate of protein production [1].

tRNA-derived fragments target the small ribosomal subunit to fine-tune translation

Post-transcriptional cleavage of RNA molecules to generate smaller fragments is a widespread mechanism that enlarges the structural and functional complexity of cellular RNomes. In particular, fragments deriving from both precursor and mature tRNAs represent one of the rapidly growing classes of post-transcriptional RNA pieces. Importantly, these tRNA-derived fragments (tRFs) possess distinct expression patterns, abundance, cellular localizations, or biological roles compared with their parental tRNA molecules [1]. Here we present evidence that tRFs from the archaeon Haloferax volcanii directly bind to ribosomes. In a previous genomic screen for ribosome-associated small RNAs we have identified a 26 residue long fragment originating from the 5’ part of valine tRNA (Val-tRF) to be by far the most abundant tRF in H. volcanii [2]. The Val-tRF is processed in a stress- dependent manner and was found to primarily target the small ribosomal subunit in vitro and in vivo. Translational activity was markedly reduced in the presence of Val-tRF, while control RNA fragments of similar length did not show inhibition of protein biosynthesis. Crosslinking experiments and subsequent primer extension analyses revealed the Val-tRF interaction site to surround the mRNA path in the 30S subunit. In support of this, binding experiments demonstrated that Val-tRF does compete with mRNAs for ribosome binding. Therefore this tRF represents a ribosome-associated non-protein-coding RNA (rancRNA) capable of regulating gene expression in H. volcanii under environmental stress conditions probably by fine-tuning the rate of protein production [3].

tRNA-derived fragments target the small ribosomal subunit to fine-tune translation

Post-transcriptional cleavage of RNA molecules to generate smaller fragments is a widespread mechanism that enlarges the structural and functional complexity of cellular RNomes. In particular, fragments deriving from both precursor and mature tRNAs represent one of the rapidly growing classes of post-transcriptional RNA pieces. Importantly, these tRNA-derived fragments (tRFs) possess distinct expression patterns, abundance, cellular localizations, or biological roles compared with their parental tRNA molecules [1]. Here we present evidence that tRFs from the halophilic archaeon Haloferax volcanii directly bind to ribosomes. In a previous genomic screen for ribosome-associated small RNAs we have identified a 26 residue long fragment originating from the 5’ part of valine tRNA (Val-tRF) to be by far the most abundant tRF in H. volcanii [2]. The Val-tRF is processed in a stress-dependent manner and was found to primarily target the small ribosomal subunit in vitro and in vivo. Translational activity was markedly reduced in the presence of Val-tRF, while control RNA fragments of similar length did not show inhibition of protein biosynthesis. Crosslinking experiments and subsequent primer extension analyses revealed the Val-tRF interaction site to surround the mRNA path in the 30S subunit. In support of this, binding experiments demonstrated that Val-tRF does compete with mRNAs for ribosome binding. Therefore this tRF represents a ribosome-associated non-coding RNA (rancRNA) capable of regulating gene expression in H. volcanii under environmental stress conditions probably by fine-tuning the rate of protein production [3].

Osteotomy of the greater trochanter: effect on gluteus medius function

PURPOSE Advancement of the greater trochanter alters the function of the gluteus medius muscle. However, with the exception of clinical studies and biomechanical lever arm studies, no publications that analyze the consequences of advancement of the greater trochanter on the muscle function exist. The aim of the study was to analyze the mechanical changes of gluteus medius after osteotomy of the greater trochanter in a lab setting. METHODS An anatomical study of origin and insertion of the gluteus medius was carried out on four hips. Based on the dissections, a string model was developed dividing the muscle into five sectors. Changes in muscle fiber length were measured for every 10° of flexion, internal and external rotation and abduction with the trochanter in anatomic, proximalized and distalized positions. RESULTS Distalization of the trochanter leads to an imbalance of muscle action, moving the isometric sector of the muscle anteriorly with more muscle sectors being active during flexion and less during extension. Stretching of the muscle increases passive forces but decreases the force generation capacity of the muscle and at the same time increased muscle fiber excursion may require more energy consumption, which may explain earlier fatigue of the abductor musculature after distalization of the trochanter. For abduction, distalization of the muscle attachment leads to a change in contraction pattern from isometric to isotonic. Optimal balancing and excursion of the muscle is when the tip of the greater trochanter is at level with the hip rotation center. CONCLUSIONS In hips with high riding trochanter, the optimal position is at the level of the center of hip rotation. Excessive distalization should be avoided. As the conclusions and considerations are based on a lab setting, transfer to clinical practice may not necessarily apply.

Pitfalls and premature failure of the Freedom SOLO stentless valve

Gebiet: Chirurgie Abstract: Objectives This study reports a series of pitfalls, premature failures and explantations of the third generation Freedom SOLO bovine pericardial stentless valve. – – Methods 149 patients underwent aortic valve replacement (AVR) using the FS. Follow-up was 100% complete with an average observation time of 5.5±2.3 years (max. 8.7 years) and a total of 825 patient years. Following intraoperative documentation, all explanted valve prostheses underwent histological examination. – – Results Freedom from structural valve deterioration (SVD) at 5, 6, 7, 8 and 9 years was 92%, 88%, 80% and 70% and 62%, respectively. 14 prostheses required explantation due to valve-independent dysfunction (n=5, i.e. thrombus formation, oversizing, aortic dilatation, endocarditis and suture dehiscence) or valve-dependent failure (acute leaflet tears, n=4, severe stenosis, n=5). Thus freedom from explantation at 5, 6, 7, 8 and 9 years was 95%, 94%, 91% and 81% and 72%, respectively. An acute vertical tear along the non-coronary/right-coronary commissure to the base occurred at a mean of 6.0 years [range 4.3?7.3 years] and affected size 25 and 27 prostheses exclusively. Four FS required explantation after a mean of 7.5 years [range 7.0?8.3 years] due to severe functional stenosis and gross calcification that included the entire aortic root. – – Conclusions The Freedom SOLO stentless valve is safe to implant and shows satisfying mid-term results in our single institution experience. Freedom from SVD and explantation decreased markedly after only 6 ? 7 years, so that patients with FS require close observation and follow-up. Exact sizing, symmetric positioning and observing patient limitations are crucial for optimal outcome.

Comparison of zotarolimus- and everolimus-eluting coronary stents: final 5-year report of the RESOLUTE all-comers trial

BACKGROUND Newer-generation drug-eluting stents that release zotarolimus or everolimus have been shown to be superior to the first-generation drug-eluting stents. However, data comparing long-term safety and efficacy of zotarolimus- (ZES) and everolimus-eluting stents (EES) are limited. RESOLUTE all-comers (Randomized Comparison of a Zotarolimus-Eluting Stent With an Everolimus-Eluting Stent for Percutaneous Coronary Intervention) trial compared these 2 stents and has shown that ZES was noninferior to EES at 12-month for the primary end point of target lesion failure. We report the secondary clinical outcomes at the final 5-year follow-up of this trial. METHODS AND RESULTS RESOLUTE all-comer clinical study is a prospective, multicentre, randomized, 2-arm, open-label, noninferiority trial with minimal exclusion criteria. Patients (n=2292) were randomly assigned to treatment with either ZES (n=1140) or EES (n=1152). Patient-oriented composite end point (combination of all-cause mortality, myocardial infarction, and any revascularizations), device-oriented composite end point (combination of cardiac death, target vessel myocardial infarction, and clinically indicated target lesion revascularization), and major adverse cardiac events (combination of all-cause death, all myocardial infarction, emergent coronary bypass surgery, or clinically indicated target lesion revascularization) were analyzed at 5-year follow-up. The 2 groups were well-matched at baseline. Five-year follow-up data were available for 98% patients. There were no differences in patient-oriented composite end point (ZES 35.3% versus EES 32.0%, P=0.11), device-oriented composite end point (ZES 17.0% versus EES 16.2%, P=0.61), major adverse cardiac events (ZES 21.9% versus EES 21.6%, P=0.88), and definite/probable stent thrombosis (ZES 2.8% versus EES 1.8%, P=0.12). CONCLUSIONS At 5-year follow-up, ZES and EES had similar efficacy and safety in a population of patients who had minimal exclusion criteria. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT00617084.

Characterization of the Putative Xyloglucan Glycosyltransferase GT14 in Arabidopsis thaliana

Plant cell walls largely consist of matrix polysaccharides that are linked to cellulose microfibrils. Xyloglucan, the primary hemicellulose of the cell wall matrix, consists of a repeating glucose tetramer structure with xylose residues attached to the first three units ('XXXG'). In Arabidopsis thaliana, the core XXXG structure is further modified by enzymatic addition of galactose and fucose residues to the xylose side chains to produce XLXG, XXLG, XLLG and XLFG structures. GT14 is a putative glycosyltransferase in the GT47 gene family. Initial predictions of GT14's hydrophobic regions, based on its translated amino acid sequence, are almost identical to its Arabidopsis homolog MUR3, which is a xyloglucan galactosyltransferase targeted to the Golgi membrane. This suggests that, like MUR3, GT14 possesses a transmembrane domain and that it is targeted to the Golgi. The monosaccharide composition of leaves from T-DNA insertion knockouts of GT14 was analyzed by gas-liquid chromatography. The gt14 plants were found to have lower fucose and higher mannose contents than wild type plants. Analysis of cell wall and soluble fractions from gt14 and wild type plants revealed that most of the deficiency in fucose was accounted for in the cell wall, supporting the idea that GT14's target is xyloglucan. Finally, gt14 and wild type plants were transformed with GT14 for complementation and overexpression analysis. The majority of transformed plants did not show significant changes with regard to monosaccharide composition. This may be because the plants were in the T1 generation and, thus, hemizygous. Analysis of homozygous plants in the T2 generation may reveal noticeable changes. Further studies on the xyloglucan composition of gt14 plants are necessary to put the observed reduction in cell wall fucose into a meaningful context.

Cross -packing among retroviruses and characterization of the feline immunodeficiency virus (FIV) packaging signal: Implications for the development of FIV-based gene transfer systems

Feline immunodeficiency virus (FIV)-based gene transfer systems are being seriously considered for human gene therapy as an alternative to vectors based on primate lentiviruses, a genetically complex group of retroviruses capable of infecting non-dividing cells. The greater phylogenetic distance between the feline and primate lentiviruses is thought to reduce chances of the generation of recombinant viruses. However, safety of FIV-based vector systems has not been tested experimentally. Since primate lentiviruses such as human and simian immunodeficiency viruses (HIV/SIV) can cross-package each other's genomes, we tested this trait with respect to FIV. Unexpectedly, both feline and primate lentiviruses were reciprocally able to both cross-package and propagate each other's RNA genomes. This was largely due to the recognition of viral packaging signals by the heterologous proteins. However, a simple retrovirus such as Mason-Pfizer monkey virus (MPMV) was unable to package FIV RNA. Interestingly, FIV could package MPMV RNA, but not propagate it for further steps of replication. These findings suggest that upon co-infection of the same host, cross-packaging may allow distinct retroviruses to generate chimeric variants with unknown pathogenic potential. ^ In order to understand the packaging determinants in FIV, we conducted a detailed mutational analysis of the region thought to contain FIV packaging signal. We show that the first 90–120 nt of the 5′ untranslated region (UTR) and the first 90 nt of gag were simultaneously required for efficient FIV RNA packaging. These results suggest that the primary FIV packaging signal is multipartite and discontinuous, composed of two core elements separated by 150 nt of the 5 ′UTR. ^ The above studies are being used towards the development of safer FIV-based self-inactivating (SIN) vectors. These vectors are being designed to eliminate the ability of FIV transfer vector RNAs to be mobilized by primate lentiviral proteins that may be present in the target cells. Preliminary test of the first generation of these vectors has revealed that they are incapable of being propagated by feline proteins. The inability of FIV transfer vectors to express packageable vector RNA after integration should greatly increase the safety of FIV vectors for human gene therapy. ^

Víctor Raúl Haya de la Torre, el APRA y el Indoamericanismo : Victor Raúl Haya de la Torre, the «Apra» and Indo–Americanism

El propósito de este trabajo es reflexionar sobre la importancia histórica, vigencia y protagonismo de personalidades como la de Víctor Raúl Haya de la Torre, abarcando las ideologías que pretendieron imponer sus proyectos y discursos políticos occidentales en la región. Para referirse al aprismo y al indoamericanismo, es menester preguntarse sobre la densidad romántica de las motivaciones que tuvieron los revolucionarios del siglo XIX y de los de la década del 30 para ejercer sus derechos ciudadanos en tiempos de colonización, dependencia y emancipación en medio de los rudimentarios influjos de la modernización. Preguntarse por qué en aquellos tiempos la Patria era Vida y Muerte, fuente de identidad primordial; qué estaban pensando los ideólogos norteamericanos en las últimas décadas del siglo XIX acerca de América Latina y luego dirigir nuestra mirada a Perú, su círculo serrano y costeño como espacio de contradicción migratoria e intercultural.

Composition of minerals and rocks from the Markov Deep, Central Atlantic

The paper presents materials on composition and texture of weakly serpentinized ultrabasic rocks from the western and eastern walls of the Markov Deep (5°30.6'-5°32.4'N) in the rift valley of the Mid-Atlantic Ridge. Predominant harzburgites with protogranular and porphyroclastic textures contain two major generations of minerals: the first generation composes the bulk of rocks and consists of Ol_89.8-90.4 + En_90.2-90.8 + Di_91.8 + Chr (Cr#32.3-36.6, Mg#67.2-70.0), while the second generation composes very thin branching veinlets and consists of PlAn_32-47 + Ol_74.3-77.1 + Opx_55.7-71.9 + Cpx_67.5 + Amph_53.7-74.2 + Ilm. Syndeformational olivine neoblasts in recrystallization zones are highly magnesian. Concentrations and covariations of major elements in harzburgites indicate that these rocks are depleted in mantle residues (high Mg# of minerals and whole-rock samples and low in CaO, Al2O3, and TiO2) that are significantly enriched in trace HFSE and REE (Zr, Hf, Y, LREE, and all REE). Mineralogy and geochemistry of harzburgites were formed by interaction of mantle residues with hydrous, strongly fractionated melts that impregnated them. Mineral composition of veinlets in harzburgites and mineralogical-geochemical characteristics of related plagiogranites and gabbronorites suggest that these plagiogranites were produced by melt residuals after crystallization of gabbronorites. Modern characteristics of harzburgites were shaped by the following processes: (i) partial melting of mantle material simultaneously with its subsolidus deformations, (ii) brittle-plastic deformations associated with cataclastic flow and recrystallization, and (iii) melt percolation along zones of maximal stress relief and interaction of this melt with magnesian mantle residue.

Organic geochemistry of deep sea sediments from the Nankai Trough and the Southwest Japan forearc region

Earth's largest reactive carbon pool, marine sedimentary organic matter, becomes increasingly recalcitrant during burial, making it almost inaccessible as a substrate for microorganisms, and thereby limiting metabolic activity in the deep biosphere. Because elevated temperature acting over geological time leads to the massive thermal breakdown of the organic matter into volatiles, including petroleum, the question arises whether microorganisms can directly utilize these maturation products as a substrate. While migrated thermogenic fluids are known to sustain microbial consortia in shallow sediments, an in situ coupling of abiotic generation and microbial utilization has not been demonstrated. Here we show, using a combination of basin modelling, kinetic modelling, geomicrobiology and biogeochemistry, that microorganisms inhabit the active generation zone in the Nankai Trough, offshore Japan. Three sites from ODP Leg 190 have been evaluated, namely 1173, 1174 and 1177, drilled in nearly undeformed Quaternary and Tertiary sedimentary sequences seaward of the Nankai Trough itself. Paleotemperatures were reconstructed based on subsidence profiles, compaction modelling, present-day heat flow, downhole temperature measurements and organic maturity parameters. Today's heat flow distribution can be considered mainly conductive, and is extremely high in places, reaching 180 mW/m**2. The kinetic parameters describing total hydrocarbon generation, determined by laboratory pyrolysis experiments, were utilized by the model in order to predict the timing of generation in time and space. The model predicts that the onset of present day generation lies between 300 and 500 m below sea floor (5100-5300 m below mean sea level), depending on well location. In the case of Site 1174, 5-10% conversion has taken place by a present day temperature of ca. 85 °C. Predictions were largely validated by on-site hydrocarbon gas measurements. Viable organisms in the same depth range have been proven using 14C-radiolabelled substrates for methanogenesis, bacterial cell counts and intact phospholipids. Altogether, these results point to an overlap of abiotic thermal degradation reactions going on in the same part of the sedimentary column as where a deep biosphere exists. The organic matter preserved in Nankai Trough sediments is of the type that generates putative feedstocks for microbial activity, namely oxygenated compounds and hydrocarbons. Furthermore, the rates of thermal degradation calculated from the kinetic model closely resemble rates of respiration and electron donor consumption independently measured in other deep biosphere environments. We deduce that abiotically driven degradation reactions have provided substrates for microbial activity in deep sediments at this convergent continental margin.

Photosynthetically active radiation during the experiment, and lipid content of sub- and intertidal specimens of the endemic Antarctic red alga, Palmaria decipiens

In coastal waters, Antarctic rhodophytes are exposed to harsh environmental conditions throughout the year, like low water temperatures ranging from -1.8°C to 2°C and high light during the summer season. Photosynthetic performance under these conditions may be affected by slowed down enzymatic reactions and the increased generation of reactive oxygen species. The consequence might be a chronic photoinhibition of photosynthetic primary reactions related to increased fragmentation of the D1 reaction centre protein in photosystem II. It is hypothesized that changes in lipid composition of biomembranes may represent an adaptive trait to maintain D1 turnover in response to temperature variation. The interactive effects of high light and low temperature were studied on an endemic Antarctic red alga, Palmaria decipiens, sampled from two shore levels, intertidal and subtidal, and exposed to mesocosm experiments using two levels of natural solar radiation and two different temperature regimes (2-5°C and 5-10°C). During the experimental period of 23 days, maximum quantum yield of photosynthesis decreased in all treatments, with the intertidal specimens exposed at 5-10°C being most affected. On the pigment level, a decreasing ratio of phycobiliproteins to chlorophyll a was found in all treatments. A pronounced decrease in D1 protein concentration occurred in subtidal specimens exposed at 2-5°C. Marked changes in lipid composition, i.e. the ratio of saturated to unsaturated fatty acids, indicated an effective response of specimens to temperature change. Results provide new insights into mechanisms of stress adaptation in this key species of shallow Antarctic benthic communities.