Translation factor and RNA binding protein mRNA interactomes support broader RNA regulons for posttranscriptional control.

The regulation of translation provides a rapid and direct mechanism to modulate the cellular proteome. In eukaryotes, an established model for the recruitment of ribosomes to mRNA depends upon a set of conserved translation initiation factors. Nevertheless, how cells orchestrate and define the selection of individual mRNAs for translation, as opposed to other potential cytosolic fates, is poorly understood.

Interaction of the La-related protein Slf1 with colliding ribosomes maintains translation of oxidative-stress responsive mRNAs.

In response to oxidative stress cells reprogram gene expression to enhance levels of antioxidant enzymes and promote survival. In Saccharomyces cerevisiae the polysome-interacting La-related proteins (LARPs) Slf1 and Sro9 aid adaptation of protein synthesis during stress by undetermined means. To gain insight in their mechanisms of action in stress responses, we determined LARP mRNA binding positions in stressed and unstressed cells.

Quantifying the Binding of Fluorescently Labeled Guanine Nucleotides and Initiator tRNA to Eukaryotic Translation Initiation Factor 2.

The translation initiation factor eIF2 is critical for protein synthesis initiation, and its regulation is central to the integrated stress response (ISR). eIF2 is a G protein, and the activity is regulated by its GDP or GTP-binding status, such that only GTP-bound eIF2 has high affinity for initiator methionyl tRNA. In the ISR, regulatory signaling reduces the availability of eIF2-GTP and so downregulates protein synthesis initiation in cells.

GTP binding to translation factor eIF2B stimulates its guanine nucleotide exchange activity.

eIF2B is the guanine nucleotide exchange factor (GEF) required for cytoplasmic protein synthesis initiation in eukaryotes and its regulation within the integrated stress response (ISR). It activates its partner factor eIF2, thereby promoting translation initiation. Here we provide evidence through biochemical and genetic approaches that eIF2B can bind directly to GTP and this can enhance its rate of GEF activity toward eIF2-GDP .

Integrated multi-omics reveals common properties underlying stress granule and P-body formation.

Non-membrane-bound compartments such as P-bodies (PBs) and stress granules (SGs) play important roles in the regulation of gene expression following environmental stresses. We have systematically and quantitatively determined the protein and mRNA composition of PBs and SGs formed before and after nutrient stress. We find that high molecular weight (HMW) complexes exist prior to glucose depletion that we propose may act as seeds for further condensation of proteins forming mature PBs and SGs.

Overlapping regions of Caf20 mediate its interactions with the mRNA-5'cap-binding protein eIF4E and with ribosomes.

By interacting with the mRNA 5' cap, the translation initiation factor eIF4E plays a critical role in selecting mRNAs for protein synthesis in eukaryotic cells. Caf20 is a member of the family of proteins found across eukaryotes termed 4E-BPs, which compete with eIF4G for interaction with eIF4E. Caf20 independently interacts with ribosomes.

Impaired eIF5A function causes a Mendelian disorder that is partially rescued in model systems by spermidine.

The structure of proline prevents it from adopting an optimal position for rapid protein synthesis. Poly-proline-tract (PPT) associated ribosomal stalling is resolved by highly conserved eIF5A, the only protein to contain the amino acid hypusine. We show that de novo heterozygous EIF5A variants cause a disorder characterized by variable combinations of developmental delay, microcephaly, micrognathia and dysmorphism.

The structural basis of translational control by eIF2 phosphorylation.

Protein synthesis in eukaryotes is controlled by signals and stresses via a common pathway, called the integrated stress response (ISR). Phosphorylation of the translation initiation factor eIF2 alpha at a conserved serine residue mediates translational control at the ISR core. To provide insight into the mechanism of translational control we have determined the structures of eIF2 both in phosphorylated and unphosphorylated forms bound with its nucleotide exchange factor eIF2B by electron cryomicroscopy.

The Influence of Angler Values, Involvement, Catch Orientation, Satisfaction, Agency Trust, and Demographics on Support for Habitat Protection and Restoration Versus Stocking in Publicly Managed Waters.

Resource managers benefit from knowledge of angler support for fisheries management strategies. Factors including angler values (protection, utilitarian, and dominance), involvement (attraction, centrality, social, identity affirmation, and expression), catch-related motivations (catching some, many, and big fish, and keeping fish), satisfaction, agency trust, and demographics may relate to fisheries management preferences. Using results from a mail survey of Minnesota resident anglers, we explored how these factors were related to budget support for fish stocking relative to habitat protection/restoration.

Fail-safe control of translation initiation by dissociation of eIF2α phosphorylated ternary complexes.

Phosphorylation of eIF2α controls translation initiation by restricting the levels of active eIF2-GTP/Met-tRNAi ternary complexes (TC). This modulates the expression of all eukaryotic mRNAs and contributes to the cellular integrated stress response. Key to controlling the activity of eIF2 are translation factors eIF2B and eIF5, thought to primarily function with eIF2-GDP and TC respectively.

eIF2β is critical for eIF5-mediated GDP-dissociation inhibitor activity and translational control.

In protein synthesis translation factor eIF2 binds initiator tRNA to ribosomes and facilitates start codon selection. eIF2 GDP/GTP status is regulated by eIF5 (GAP and GDI functions) and eIF2B (GEF and GDF activities), while eIF2α phosphorylation in response to diverse signals is a major point of translational control. Here we characterize a growth suppressor mutation in eIF2β that prevents eIF5 GDI and alters cellular responses to reduced eIF2B activity, including control of GCN4 translation.

Electronic Structure of a Mixed-Metal Fluoride-Centered Triangle Complex: A Potential Qubit Component.

A novel fluoride-centered triangular-bridged carboxylate complex, [Ni2Cr(μ3-F)(O2C(t)Bu)6(HO2C(t)Bu)3] (1), is reported. Simple postsynthetic substitution of the terminal pivalic acids in 1 with pyridine and 4-methylpyridine led to the isolation of [Ni2Cr(μ3-F)(O2C(t)Bu)6(C5H5N)3] (2) and [Ni2Cr(μ3-F)(O2C(t)Bu)6((4-CH3)C5H4N)3] (3). Structural and magnetic characterizations carried out on the series reveal a dominating antiferromagnetic interaction between the nickel and chromium centers leading to an S = (1)/2 ground state with a very unusual value of geff = 2.

A new function and complexity for protein translation initiation factor eIF2B.

eIF2B is a multisubunit protein that is critical for protein synthesis initiation and its control. It is a guanine nucleotide exchange factor (GEF) for its GTP-binding protein partner eIF2. eIF2 binds initiator tRNA to ribosomes and promotes mRNA AUG codon recognition.

eIF2B is a decameric guanine nucleotide exchange factor with a γ2ε2 tetrameric core.

eIF2B facilitates and controls protein synthesis in eukaryotes by mediating guanine nucleotide exchange on its partner eIF2. We combined mass spectrometry (MS) with chemical cross-linking, surface accessibility measurements and homology modelling to define subunit stoichiometry and interactions within eIF2B and eIF2. Although it is generally accepted that eIF2B is a pentamer of five non-identical subunits (α-ε), here we show that eIF2B is a decamer.

eIF2B promotes eIF5 dissociation from eIF2*GDP to facilitate guanine nucleotide exchange for translation initiation.

Protein synthesis factor eIF2 delivers initiator tRNA to the ribosome. Two proteins regulate its G-protein cycle: eIF5 has both GTPase-accelerating protein (GAP) and GDP dissociation inhibitor (GDI) functions, and eIF2B is the guanine nucleotide exchange factor (GEF). In this study, we used protein-protein interaction and nucleotide exchange assays to monitor the kinetics of eIF2 release from the eIF2•GDP/eIF5 GDI complex and determine the effect of eIF2B on this release.

Mechanisms of translational regulation by a human eIF5-mimic protein.

The translation factor eIF5 is an important partner of eIF2, directly modulating its function in several critical steps. First, eIF5 binds eIF2/GTP/Met-tRNA(i)(Met) ternary complex (TC), promoting its recruitment to 40S ribosomal subunits. Secondly, its GTPase activating function promotes eIF2 dissociation for ribosomal subunit joining.

eIF5 is a dual function GAP and GDI for eukaryotic translational control.

We recently showed in a publication in Nature that the eukaryotic translation initiation factor eIF5 has a second regulatory function and is a GDI (GDP dissociation inhibitor) in addition to its previously characterized role as a GAP (GTPase accelerating protein). These findings provide new insight into the mechanism of translation initiation in eukaryotic cells. Additional findings show that the GDI function is critical for the normal regulation of protein synthesis by phosphorylation of eIF2α at ser51.

Su(dx) E3 ubiquitin ligase-dependent and -independent functions of polychaetoid, the Drosophila ZO-1 homologue.

Zona occludens (ZO) proteins are molecular scaffolds localized to cell junctions, which regulate epithelial integrity in mammals. Using newly generated null alleles, we demonstrate that polychaetoid (pyd), the unique Drosophila melanogaster ZO homologue, regulates accumulation of adherens junction-localized receptors, such as Notch, although it is dispensable for epithelial polarization. Pyd positively regulates Notch signaling during sensory organ development but acts negatively on Notch to restrict the ovary germline stem cell niche.

eIF5 has GDI activity necessary for translational control by eIF2 phosphorylation.

In protein synthesis initiation, the eukaryotic translation initiation factor (eIF) 2 (a G protein) functions in its GTP-bound state to deliver initiator methionyl-tRNA (tRNA(i)(Met)) to the small ribosomal subunit and is necessary for protein synthesis in all cells. Phosphorylation of eIF2 [eIF2(alphaP)] is critical for translational control in diverse settings including nutrient deprivation, viral infection and memory formation. eIF5 functions in start site selection as a GTPase accelerating protein (GAP) for the eIF2.

Clues to the mechanism of action of eIF2B, the guanine-nucleotide-exchange factor for translation initiation.

A variety of cellular processes rely on G-proteins, which cycle through active GTP-bound and inactive GDP-bound forms. The switch between these states is commonly regulated by GEFs (guanine-nucleotide-exchange factors) and GAPs (GTPase-activating proteins). Although G-proteins have structural similarity, GEFs are very diverse proteins.

Specificity and autoregulation of Notch binding by tandem WW domains in suppressor of Deltex.

WW domains target proline-tyrosine (PY) motifs and frequently function as tandem pairs. When studied in isolation, single WW domains are notably promiscuous and regulatory mechanisms are undoubtedly required to ensure selective interactions. Here, we show that the fourth WW domain (WW4) of Suppressor of Deltex, a modular Nedd4-like protein that down-regulates the Notch receptor, is the primary mediator of a direct interaction with a Notch-PY motif.

Policy challenges from the "White" Senate inquiry into workplace-related health impacts of toxic dusts and nanoparticles.

On 22 June 2005 the Senate of the Commonwealth of Australia voted to establish an inquiry into workplace harm related to toxic dust and emerging technologies (including nanoparticles). The inquiry became known as the "White" Inquiry after Mr Richard White, a financially uncompensated sufferer of industrial sandblasting-induced lung disease who was instrumental in its establishment. The "White" Inquiry delivered its final report and recommendations on 31 May 2006.