The conserved transcriptional regulator heat shock factor 1 (Hsf1) is a key sensor of proteotoxic and other stress in the eukaryotic cytosol. We surveyed Hsf1 activity in a genome-wide ...loss-of-function library in Saccaromyces cerevisiae as well as ∼78,000 double mutants and found Hsf1 activity to be modulated by highly diverse stresses. These included disruption of a ribosome-bound complex we named the Ribosome Quality Control Complex (RQC) comprising the Ltn1 E3 ubiquitin ligase, two highly conserved but poorly characterized proteins (Tae2 and Rqc1), and Cdc48 and its cofactors. Electron microscopy and biochemical analyses revealed that the RQC forms a stable complex with 60S ribosomal subunits containing stalled polypeptides and triggers their degradation. A negative feedback loop regulates the RQC, and Hsf1 senses an RQC-mediated translation-stress signal distinctly from other stresses. Our work reveals the range of stresses Hsf1 monitors and elucidates a conserved cotranslational protein quality control mechanism.
Display omitted
► Comprehensive characterization of the stresses sensed by Hsf1 ► Characterization of a complex that targets ribosomes stalled at translation ► An autoregulatory loop regulates activity of the complex ► Discovery of a translation-stress signaling pathway from the ribosome to Hsf1
A ribosome-bound complex designated RQC associates with 60S ribosomal subunits containing stalled polypeptides to trigger their degradation.
A good model of object shape is essential in applications such as segmentation, detection, inpainting and graphics. For example, when performing segmentation, local constraints on the shapes can help ...where object boundaries are noisy or unclear, and global constraints can resolve ambiguities where background clutter looks similar to parts of the objects. In general, the stronger the model of shape, the more performance is improved. In this paper, we use a type of deep Boltzmann machine (Salakhutdinov and Hinton, International Conference on Artificial Intelligence and Statistics,
2009
) that we call a Shape Boltzmann Machine (SBM) for the task of modeling foreground/background (binary) and parts-based (categorical) shape images. We show that the SBM characterizes a
strong
model of shape, in that samples from the model look realistic and it can generalize to generate samples that differ from training examples. We find that the SBM learns distributions that are qualitatively and quantitatively better than existing models for this task.
Abstract This review highlights the synthesis, properties, and advanced applications of synthetic and natural polymers 3D printed using stereolithography for soft tissue engineering applications. ...Soft tissue scaffolds are of great interest due to the number of musculoskeletal, cardiovascular, and connective tissue injuries and replacements humans face each year. Accurately replacing or repairing these tissues is challenging due to the variation in size, shape, and strength of different types of soft tissue. With advancing processing techniques such as stereolithography, control of scaffold resolution down to the μm scale is achievable along with the ability to customize each fabricated scaffold to match the targeted replacement tissue. Matching the advanced manufacturing technique to polymer properties as well as maintaining the proper chemical, biological, and mechanical properties for tissue replacement is extremely challenging. This review discusses the design of polymers with tailored structure, architecture, and functionality for stereolithography, while maintaining chemical, biological, and mechanical properties to mimic a broad range of soft tissue types.
Display omitted
Vat Photopolymerization (stereolithography, SLA), an Additive Manufacturing (AM) or 3D printing technology, holds particular promise for the fabrication of tissue scaffolds for use in ...regenerative medicine. Unlike traditional tissue scaffold fabrication techniques, SLA is capable of fabricating designed scaffolds through the selective photopolymerization of a photopolymer resin on the micron scale. SLA offers unprecedented control over scaffold porosity and permeability, as well as pore size, shape, and interconnectivity. Perhaps even more significantly, SLA can be used to fabricate vascular networks that may encourage angio and vasculogenesis. Fulfilling this potential requires the development of new photopolymers, the incorporation of biochemical factors into printed scaffolds, and an understanding of the effects scaffold geometry have on cell viability, proliferation, and differentiation. This review compares SLA to other scaffold fabrication techniques, highlights significant advances in the field, and offers a perspective on the field’s challenges and future directions.
Engineering de novo tissues continues to be challenging due, in part, to our inability to fabricate complex tissue scaffolds that can support cell proliferation and encourage the formation of developed tissue. The goal of this review is to first introduce the reader to traditional and Additive Manufacturing scaffold fabrication techniques. The bulk of this review will then focus on apprising the reader of current research and provide a perspective on the promising use of vat photopolymerization (stereolithography, SLA) for the fabrication of complex tissue scaffolds.
Purpose
– The purpose of this paper is to explore the use of binder jetting to fabricate high-purity copper parts. The ability to fabricate geometrically complex copper shapes would have implications ...on the design and manufacture of components for thermal management systems and structural electronics.
Design/methodology/approach
– To explore the feasibility of processing copper via binder jetting, the authors followed an established material development process that encompasses powder selection and tuning process parameters in printing and thermal cycles. Specifically, the authors varied powder size and sintering cycles to explore their effects on densification.
Findings
– Three differently sized copper powders were successfully printed, followed by sintering in a reducing atmosphere. It was found that a 15-μm-diameter powder with a sintering cycle featuring a 1,080°C maximum temperature provides the most dense (85 per cent) and pure (97 per cent) final copper parts of the parameters tested.
Research limitations/implications
– Due to powder-based additive manufacturing techniques’ inherent limitations in powder packing and particle size diameter, there are difficulties in creating fully dense copper parts. To improve thermal, electrical and mechanical properties, future work will focus on improving densification.
Originality/value
– The paper demonstrates the first use of binder jetting to fabricate copper artifacts. The resulting copper parts are denser than what is typically found in binder jetting of metal powders (without infiltration); significant opportunity remains to further optimize the manufacturing process by introducing novel techniques to tailor the material properties for thermal/electrical applications.
Nearly all mitochondrial proteins are nuclear-encoded and are targeted to their mitochondrial destination from the cytosol. Here, we used proximity-specific ribosome profiling to comprehensively ...measure translation at the mitochondrial surface in yeast. Most inner-membrane proteins were cotranslationally targeted to mitochondria, reminiscent of proteins entering the endoplasmic reticulum (ER). Comparison between mitochondrial and ER localization demonstrated that the vast majority of proteins were targeted to a specific organelle. A prominent exception was the fumarate reductase Osm1, known to reside in mitochondria. We identified a conserved ER isoform of Osm1, which contributes to the oxidative protein-folding capacity of the organelle. This dual localization was enabled by alternative translation initiation sites encoding distinct targeting signals. These findings highlight the exquisite in vivo specificity of organellar targeting mechanisms.
Display omitted
Elastomers are a unique and important class of polymers that enjoy applications in virtually every industry, including healthcare, aerospace, automotive, and apparel. However, due to ...inherent physical, thermal, and mechanical properties of elastomers, the additive manufacturing (AM) of elastomers remains challenging. These challenges are discussed in the context of various AM processes, including powder bed fusion, material extrusion, and vat photopolymerization. This review provides an in-depth discussion of the current state of silicone and polyurethane polymers for AM, and also discusses polyesters/polycarbonates, liquid crystalline elastomers, and monomer compositions that provide elastomeric properties upon photocuring. Finally, the current state of common, commercially-available elastomers for AM is provided, as well as an outlook for this rapidly progressing field. We expect this review to be useful for any research involved with the additive manufacturing of elastomers.
The results of cognate docking with the prepared Astex dataset provided by the organizers of the “Docking and Scoring: A Review of Docking Programs” session at the 241st ACS national meeting are ...presented. The MOE software with the newly developed GBVI/WSA dG scoring function is used throughout the study. For 80 % of the Astex targets, the MOE docker produces a top-scoring pose within 2 Å of the X-ray structure. For 91 % of the targets a pose within 2 Å of the X-ray structure is produced in the top 30 poses. Docking failures, defined as cases where the top scoring pose is greater than 2 Å from the experimental structure, are shown to be largely due to the absence of bound waters in the source dataset, highlighting the need to include these and other crucial information in future standardized sets. Docking success is shown to depend heavily on data preparation. A “dataset preparation” error of 0.5 kcal/mol is shown to cause fluctuations of over 20 % in docking success rates.
PDF
