Translation controlled

A report of the meeting 'Translational Control', Cold Spring Harbor, USA, 3-7 September 2008

Dynamic cycling of eIF2 through a large eIF2B-containing cytoplasmic body: implications for translation control

The eukaryotic translation initiation factor 2B (eIF2B) provides a fundamental controlled point in the pathway of protein synthesis. eIF2B is the heteropentameric guanine nucleotide exchange factor that converts eIF2, from an inactive guanosine diphosphate–bound complex to eIF2-guanosine triphosphate. This reaction is controlled in response to a variety of cellular stresses to allow the rapid reprogramming of cellular gene expression. Here we demonstrate that in contrast to other translation initiation factors, eIF2B and eIF2 colocalize to a specific cytoplasmic locus. The dynamic nature of this locus is revealed through fluorescence recovery after photobleaching analysis. Indeed eIF2 shuttles into these foci whereas eIF2B remains largely resident. Three different strategies to decrease the guanine nucleotide exchange function of eIF2B all inhibit eIF2 shuttling into the foci. These results implicate a defined cytoplasmic center of eIF2B in the exchange of guanine nucleotides on the eIF2 translation initiation factor. A focused core of eIF2B guanine nucleotide exchange might allow either greater activity or control of this elementary conserved step in the translation pathway

Cellular eIF2B subunit localisation: implications for the integrated stress response and its control by small molecule drugs

eIF2 is a G protein critical for translation. It is tightly regulated in the integrated stress response (ISR) via phosphorylation of eIF2α and the subsequent control of eIF2B, a multisubunit guanine nucleotide exchange factor (GEF). Through studying the localisation of eIF2B subunits we identified cytoplasmic eIF2B bodies in mammalian cells. We highlight a relationship between body size and the eIF2B subunits localising to them; larger bodies contain all subunits and smaller bodies contain predominantly catalytic subunits. eIF2 localises to eIF2B bodies and shuttles within these bodies in a manner which correlates with eIF2B activity. Upon stress eIF2α-P localises predominately to larger bodies and results in a decreased shuttling of eIF2. Interestingly drugs which inhibit the ISR can rescue eIF2 shuttling in a manner correlating to levels of eIF2α-P. In contrast, smaller bodies show increased eIF2 shuttling in response to stress, which is accompanied by the localisation of eIF2Bδ to these bodies, suggesting the formation of a novel trimeric complex of eIF2B. This response is mimicked by ISR inhibiting drugs, providing insight into their potential mechanism of action. This study provides evidence that the composition and function of mammalian eIF2B bodies is regulated by the ISR and drugs which control it

Stress-dependent relocalization of translationally primed mRNPs to cytoplasmic granules that are kinetically and spatially distinct from P-bodies

Cytoplasmic RNA granules serve key functions in the control of messenger RNA (mRNA) fate in eukaryotic cells. For instance, in yeast, severe stress induces mRNA relocalization to sites of degradation or storage called processing bodies (P-bodies). In this study, we show that the translation repression associated with glucose starvation causes the key translational mediators of mRNA recognition, eIF4E, eIF4G, and Pab1p, to resediment away from ribosomal fractions. These mediators then accumulate in P-bodies and in previously unrecognized cytoplasmic bodies, which we define as EGP-bodies. Our kinetic studies highlight the fundamental difference between EGP- and P-bodies and reflect the complex dynamics surrounding reconfiguration of the mRNA pool under stress conditions. An absence of key mRNA decay factors from EGP-bodies points toward an mRNA storage function for these bodies. Overall, this study highlights new potential control points in both the regulation of mRNA fate and the global control of translation initiation

Noisy Coherent Population Trapping: Applications to Noise Estimation and Qubit State Preparation

Coherent population trapping is a well-known quantum phenomenon in a driven $\Lambda$ system, with many applications across quantum optics. However, when a stochastic bath is present in addition to vacuum noise, the observed trapping is no longer perfect. Here we derive a time-convolutionless master equation describing the equilibration of the $\Lambda$ system in the presence of additional temporally correlated classical noise, with an unknown decay parameter. Our simulations show a one-to-one correspondence between the decay parameter and the depth of the characteristic dip in the photoluminescence spectrum, thereby enabling the unknown parameter to be estimated from the observed spectra. We apply our analysis to the problem of qubit state initialization in a $\Lambda$ system via dark states and show how the stochastic bath affects the fidelity of such initialization as a function of the desired dark-state amplitudes. We show that an optimum choice of Rabi frequencies is possible

“everything in one place”

Purpose: To describe older adults’ perspectives on a new patient education manual for the recovery process after hip fracture. Materials and methods: The Fracture Recovery for Seniors at Home (FReSH) Start manual is an evidence- based manual for older adults with fall-related hip fracture. The manual aims to support the transition from hospital to home by facilitating self- management of the recovery process. We enrolled 31 community-dwelling older adults with previous fall-related hip fracture and one family member. We collected data using a telephone-based questionnaire with eight five-point Likert items and four semi-structured open-ended questions to explore participants’ perceptions on the structure, content, and illustration of the manual. The questionnaire also asked participants to rate the overall utility (out of 10 points) and length of the manual. We used content analysis to describe main themes from responses to the open-ended interview questions. Results: Participants’ ratings for structure, content, and illustrations ranged from 4 to 5 (agree to highly agree), and the median usefulness rating was 9 (10th percentile: 7, 90th percentile: 10). Main themes from the content analysis included: ease of use and presentation; health literacy; illustration utility; health care team delivery; general impression, information support from hospital to home; emotional and decision-making support; and the novelty of the manual. Conclusion: The FReSH Start manual was perceived as comprehensive in content and acceptable for use with older adults post-fall- related hip fracture. Participants expressed a need for delivery and explanation of the manual by a health care team member

Creep Forming of Carbon-Reinforced Ceramic-Matrix Composites

A set of lecture slides describes an investigation of creep forming as a means of imparting desired curvatures to initially flat stock plates of carbon-reinforced ceramic-matrix composite (C-CMC) materials. The investigation is apparently part of a continuing effort to develop improved means of applying small CCMC repair patches to reinforced carbon-carbon leading edges of aerospace vehicles (e.g., space shuttles) prior to re-entry into the atmosphere of the Earth. According to one of the slides, creep forming would be an intermediate step in a process that would yield a fully densified, finished C-CMC part having a desired size and shape (the other steps would include preliminary machining, finish machining, densification by chemical vapor infiltration, and final coating). The investigation included experiments in which C-CMC disks were creep-formed by heating them to unspecified high temperatures for time intervals of the order of 1 hour while they were clamped into single- and double-curvature graphite molds. The creep-formed disks were coated with an oxidation- protection material, then subjected to arc-jet tests, in which the disks exhibited no deterioration after exposure to high-temperature test conditions lasting 490 seconds

A Neuroeconomics Approach to Inferring Utility Functions in Sensorimotor Control

Making choices is a fundamental aspect of human life. For over a century experimental economists have characterized the decisions people make based on the concept of a utility function. This function increases with increasing desirability of the outcome, and people are assumed to make decisions so as to maximize utility. When utility depends on several variables, indifference curves arise that represent outcomes with identical utility that are therefore equally desirable. Whereas in economics utility is studied in terms of goods and services, the sensorimotor system may also have utility functions defining the desirability of various outcomes. Here, we investigate the indifference curves when subjects experience forces of varying magnitude and duration. Using a two-alternative forced-choice paradigm, in which subjects chose between different magnitude–duration profiles, we inferred the indifference curves and the utility function. Such a utility function defines, for example, whether subjects prefer to lift a 4-kg weight for 30 s or a 1-kg weight for a minute. The measured utility function depends nonlinearly on the force magnitude and duration and was remarkably conserved across subjects. This suggests that the utility function, a central concept in economics, may be applicable to the study of sensorimotor control