RNA Unwinding by the Trf4/Air2/Mtr4 Polyadenylation (TRAMP) Complex

Many RNA-processing events in the cell nucleus involve the Trf4/Air2/Mtr4 polyadenylation (TRAMP) complex, which contains the poly(A) polymerase Trf4p, the Zn-knuckle protein Air2p, and the RNA helicase Mtr4p. TRAMP polyadenylates RNAs designated for processing by the nuclear exosome. In addition, TRAMP functions as an exosome cofactor during RNA degradation, and it has been speculated that this role involves disruption of RNA secondary structure. However, it is unknown whether TRAMP displays RNA unwinding activity. It is also not clear how unwinding would be coordinated with polyadenylation and the function of the RNA helicase Mtr4p in modulating poly(A) addition. Here, we show that TRAMP robustly unwinds RNA duplexes. The unwinding activity of Mtr4p is significantly stimulated by Trf4p/Air2p, but the stimulation of Mtr4p does not depend on ongoing polyadenylation. Nonetheless, polyadenylation enables TRAMP to unwind RNA substrates that it otherwise cannot separate. Moreover, TRAMP displays optimal unwinding activity on substrates with a minimal Mtr4p binding site comprised of adenylates. Our results suggest a model for coordination between unwinding and polyadenylation activities by TRAMP that reveals remarkable synergy between helicase and poly(A) polymerase

Degradation of Hypomodified tRNA\u3csub\u3ei\u3c/sub\u3e\u3csup\u3eMet\u3c/sup\u3e in vivo Involves RNA-dependent ATPase Activity of the DExH Helicase Mtr4p

Effective turnover of many incorrectly processed RNAs in yeast, including hypomodified tRNAi Met, requires the TRAMP complex, which appends a short poly(A) tail to RNA designated for decay. The poly(A) tail stimulates degradation by the exosome. The TRAMP complex contains the poly(A) polymerase Trf4p, the RNA-binding protein Air2p, and the DExH RNA helicase Mtr4p. The role of Mtr4p in RNA degradation processes involving the TRAMP complex has been unclear. Here we show through a genetic analysis that MTR4 is required for degradation but not for polyadenylation of hypomodified tRNAi Met. A suppressor of the trm6-504 mutation in the tRNA m1A58 methyltransferase (Trm6p/Trm61p), which causes a reduced level of tRNAi Met, was mapped to MTR4. This mtr4-20 mutation changed a single amino acid in the conserved helicase motif VI of Mtr4p. The mutation stabilizes hypomodified tRNAi Met in vivo but has no effect on TRAMP complex stability or polyadenylation activity in vivo or in vitro. We further show that purified recombinant Mtr4p displays RNA-dependent ATPase activity and unwinds RNA duplexes with a 3′-to-5′ polarity in an ATP-dependent fashion. Unwinding and RNA-stimulated ATPase activities are strongly reduced in the recombinant mutant Mtr4-20p, suggesting that these activities of Mtr4p are critical for degradation of polyadenylated hypomodified tRNAi Met

Christa and Gerhard Wolf: Ins Ungebundene gehet eine Sehnsucht. Gesprächsraum Romantik, Prosa und Essays

Berlin and Weimar: Aufbau, 1985

Colin E. Smith: Tradition, Art and Society. Christa Wolf\u27s Prose

Essen: Die Blaue Eule, 1987. 365 p. DM 58

The RNA helicase database

RNA helicases are ubiquitous and essential enzymes that function in nearly all aspects of RNA metabolism. The RNA helicase database (www.rnahelicase.org) integrates the wealth of accumulating information on RNA helicases in a readily accessible format. The database is a portal that allows straightforward retrieval of comprehensive information on sequence, structure and on biochemical and cellular functions of all RNA helicases from the most widely used model organisms Escherichia coli, Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, mouse and human. Also included are RNA helicases from other organisms that are subject to specific investigation. The database is structured according to the most recent helicase classification into helicase superfamilies (SFs) and families, and thus emphasizes phyologenetic relations between RNA helicases as well. Information on individual RNA helicases can be accessed through various browsing routes or through text-based searches of the database

Absence of the mu-problem in grand unification

Using properties of Goldstino, we show that in generic grand unified theories with gravity-mediated supersymmetry breaking the At-problem is nonexistent. What happens is that supersymmetry breaking universally induces the shifts of the heavy fields that generate At and BAt terms. In the leading order, these are given by the mass of gravitino and are insensitive to the scale of grand unification. The mechanism works regardless whether doublet-triplet splitting is achieved via fine-tuning or not. Moreover, we illustrate this general phenomenon on explicit examples of theories that achieve doublet-triplet splitting dynamically. These include the theories with Higgs doublet as a pseudo-Goldstone boson, as well as the approach based on spontaneous decoupling of the light color triplet from quarks and leptons

The HEX-ACO-18:Developing an age-invariant HEXACO short scale using ant colony optimization

In this study, we developed an age-invariant 18-item short form of the HEXACO Personality Inventory for use in developmental personality research. We combined the item selection procedure ant colony optimization (ACO) and the model estimation approach local structural equation modeling (LSEM). ACO is a metaheuristic algorithm that evaluates items based on the quality of the resulting short scale, thus directly optimizing criteria that can only be estimated with combinations of items, such as model fit and measurement invariance. LSEM allows for model estimation and measurement invariance testing across a continuous age variable by weighting participants, rather than splitting the sample into artificial age groups. Using a HEXACO-100 dataset of N = 6,419 participants ranging from 16 to 90 years of age, we selected a short form optimized for model fit, measurement invariance, facet coverage, and balance of item keying. To achieve scalar measurement invariance and brevity, but maintain construct coverage, we selected 18 items to represent three out of four facets from each HEXACO trait domain. The resulting HEX-ACO-18 short scale showed adequate model fit and scalar measurement invariance across age. Furthermore, the usefulness and versatility of the item and person sampling procedures ACO and LSEM is demonstrated

Probing Convolutional Neural Networks for Event Reconstruction in {\gamma}-Ray Astronomy with Cherenkov Telescopes

A dramatic progress in the field of computer vision has been made in recent years by applying deep learning techniques. State-of-the-art performance in image recognition is thereby reached with Convolutional Neural Networks (CNNs). CNNs are a powerful class of artificial neural networks, characterized by requiring fewer connections and free parameters than traditional neural networks and exploiting spatial symmetries in the input data. Moreover, CNNs have the ability to automatically extract general characteristic features from data sets and create abstract data representations which can perform very robust predictions. This suggests that experiments using Cherenkov telescopes could harness these powerful machine learning algorithms to improve the analysis of particle-induced air-showers, where the properties of primary shower particles are reconstructed from shower images recorded by the telescopes. In this work, we present initial results of a CNN-based analysis for background rejection and shower reconstruction, utilizing simulation data from the H.E.S.S. experiment. We concentrate on supervised training methods and outline the influence of image sampling on the performance of the CNN-model predictions.Comment: 8 pages, 4 figures, Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Busan, Kore