Human eukaryotic translation initiation factor 4G (eIF4G) recruits mnk1 to phosphorylate eIF4E

Human eukaryotic translation initiation factor 4E (eIF4E) binds to the mRNA cap structure and interacts with eIF4G, which serves as a scaffold protein for the assembly of eIF4E and eIF4A to form the eIF4F complex. eIF4E is an important modulator of cell growth and proliferation. It is the least abundant component of the translation initiation machinery and its activity is modulated by phosphorylation and interaction with eIF4E-binding proteins (4E-BPs). One strong candidate for the eIF4E kinase is the recently cloned MAPK-activated protein kinase, Mnk1, which phosphorylates eIF4E on its physiological site Ser209 in vitro. Here we report that Mnk1 is associated with the eIF4F complex via its interaction with the C-terminal region of eIF4G. Moreover, the phosphorylation of an eIF4E mutant lacking eIF4G-binding capability is severely impaired in cells. We propose a model whereby, in addition to its role in eIF4F assembly, eIF4G provides a docking site for Mnk1 to phosphorylate eIF4E. We also show that Mnk1 interacts with the C-terminal region of the translational inhibitor p97, an eIF4G-related protein that does not bind eIF4E, raising the possibility that p97 can block phosphorylation of eIF4E by sequestering Mnk1.     

Infection and immunity mediated by the carbohydrate recognition domain of the Entamoeba histolytica Gal/GalNAc lectin

Entamoeba histolytica causes invasive amebiasis, a major parasitic disease of the developing world, whose primary symptoms are liver abscess and colitis. All strains of E. histolytica express a 260-kDa surface Gal/GalNAc lectin that is antigenically conserved and immunogenic. The lectin is required for adherence to human intestinal epithelial cells and contact-dependent killing of immune effector cells. By expression cloning, the carbohydrate recognition domain (CRD) was identified within the lectin heavy-subunit cysteine-rich region. Of interest for a hepatic parasite, the CRD had sequence identity to the receptor-binding domain of hepatocyte growth factor (HGF) and competed with HGF for binding to the c-Met HGF receptor. In an animal model of invasive disease, immunization with the CRD inhibited liver-abscess formation, yet in humans, a naturally acquired immune response against the CRD did not persist.     

Cell transformation results in the loss of the density-dependent translational regulation of the expression of fibroblast growth factor 2 isoforms

Alternative initiation of translation at three CUG and one AUG start codons leads to the synthesis of four isoforms of fibroblast growth factor 2 (FGF-2) that have distinct intracellular localizations and affect the cell phenotype differently. We show here that the expression of FGF-2 CUG-initiated isoforms decreases in a cell-density-dependent manner in normal human skin fibroblasts (HSFs) concomitantly with the FGF-2 mRNA level. In contrast, CUG-initiated FGF-2 expression is constitutive in SK-HEP-1 cells and in HSFs transformed with SV40 large T antigen. Cell transfection using a plasmid containing the FGF-2 mRNA leader fused to chloramphenicol acetyl transferase demonstrated that up-regulation of the CUG codons depends on cis-elements located in this leader. Furthermore, UV cross-linking experiments revealed a correlation between CUG codons utilization and the binding of several proteins to the mRNA leader. On the basis of the presence of an internal ribosome entry site (IRES) in the FGF-2 mRNA, we used bicistronic vectors to transfect normal and transformed cells. The density-dependent regulation in normal HSFs was cap-dependent, whereas the constitutive CUG-initiated FGF-2 expression in transformed cells occurred essentially by an IRES-dependent mechanism. Unexpectedly, the use of the AUG start codon occurred exclusively by internal entry, which suggests the presence of a second independent IRES in the FGF-2 mRNA that would be constitutive. A study of the eIF-4E levels and of the 4E-BP1 phosphorylation state at increasing cell densities showed a decrease of the eIF-4E level, concomitant with 4E-BP1 dephosphorylation in normal cells but not in transformed cells. These data point out a complex mechanism for the regulation of FGF-2 isoforms expression involving both the cap-dependent and the cap-independent initiation of translation and favor a positive role of CUG-initiated FGF-2 in cellular proliferation and transformation.     

A new 34-kilodalton isoform of human fibroblast growth factor 2 is cap dependently synthesized by using a non-AUG start codon and behaves as a survival factor

Four isoforms of human fibroblast growth factor 2 (FGF-2) result from alternative initiations of translation at three CUG start codons and one AUG start codon. Here we characterize a new 34-kDa FGF-2 isoform whose expression is initiated at a fifth initiation codon. This 34-kDa FGF-2 was identified in HeLa cells by using an N-terminal directed antibody. Its initiation codon was identified by site-directed mutagenesis as being a CUG codon located at 86 nucleotides (nt) from the FGF-2 mRNA 5' end. Both in vitro translation and COS-7 cell transfection using bicistronic RNAs demonstrated that the 34-kDa FGF-2 was exclusively expressed in a cap-dependent manner. This contrasted with the expression of the other FGF-2 isoforms of 18, 22, 22.5, and 24 kDa, which is controlled by an internal ribosome entry site (IRES). Strikingly, expression of the other FGF-2 isoforms became partly cap dependent in vitro in the presence of the 5,823-nt-long 3' untranslated region of FGF-2 mRNA. Thus, the FGF-2 mRNA can be translated both by cap-dependent and IRES-driven mechanisms, the balance between these two mechanisms modulating the ratio of the different FGF-2 isoforms. The function of the new FGF-2 was also investigated. We found that the 34-kDa FGF-2, in contrast to the other isoforms, permitted NIH 3T3 cell survival in low-serum conditions. A new arginine-rich nuclear localization sequence (NLS) in the N-terminal region of the 34-kDa FGF-2 was characterized and found to be similar to the NLS of human immunodeficiency virus type 1 Rev protein. These data suggest that the function of the 34-kDa FGF-2 is mediated by nuclear targets.     

Epidemiology of atherosclerotic peripheral arterial occlusive disease in Hong Kong

Incubation of bovine liver mitochondrial rhodanese in dilute, reducing solutions at temperatures ranging between 30 and 45 degreesC conduced to a rapid loss of enzymatic activity. This inactivation was substantially reduced in the presence of millimolar concentrations of alkali metal ions, divalent cations (including Mg2+, Ca2+, and Ba2+) were ineffective. The extent of protection afforded by monovalent cations was highly dependent on their ionic radii, with K+ and Na+ ions being the most effective protective agents. The protection afforded by a number of anions, including thiosulfate, could be totally ascribed to the presence of the accompanying monovalent cation. The overall results indicate that K+ and Na+, at concentrations and temperatures within the physiological range, substantially contribute to the stabilization of the functional structure of rhodanese.     

Optimisation of time/temperature treatment,for heat treated soft wheat flour

Chlorination of wheat flour in the EU countries has been replaced in recent years, to some extent, by heat treated flour which is used to produce high ratio cakes. Heat treated flour allows high ratio recipes to be developed which generate products with longer shelf life, finer texture, moist crumb and sweeter taste. The mechanism by which heat treatment improves the flour is not fully understood, but it is known that during the heat treatment process, protein denaturation and partial gelatinisation of the starch granules occurs, as well as an increase in batter viscosity. Therefore, it is important to optimize the flour heat treatment process, in order to enhance baking quality. Laboratory preparation of heat treated base wheat flour (culinary, soft, low protein) was carried out in a fluidised bed drier using a range of temperatures and times. The gluten was extracted from the final product and its quality was tested, to obtain objective and comparative information on the extent of protein denaturation. The results indicated that heat treatment of flour decreases gluten extensibility and partial gelatinisation of the starch granules occurred. After heat treatment the gluten appeared to retain moisture. The optimum time/temperature for the heat treatment of base flour was 120–130 °C for 30 min with moisture content of ≈12.5%.     

Improving TLB performance on current chip multiprocessor architectures through demand‐driven superpaging

Translation Lookaside Buffers (TLBs) can play a critical role in improving the performance of emerging parallel workloads. Most current chip multiprocessor systems include multilevel TLBs and provide support for superpages both at the hardware and software level. Judicious use of superpages can significantly cut down the number of TLB misses and improve overall system performance. However, indiscriminate superpage allocation results in page fragmentation and increased application footprint, which often outweigh the benefits of reduced TLB misses. Previous research has explored policies for smart allocation of superpages from an operating system perspective. This paper presents a compiler‐based strategy for automatic and profitable memory allocation via superpages. A significant advantage of a compiler‐based approach is the availability of data‐reuse information within an application. Our strategy employs data‐locality analysis to estimate the TLB demands for both single‐threaded and multi‐threaded programs and uses this metric to apply selective superpage allocation. Apart from its obvious utility in improving TLB performance, this strategy can be used to improve the effectiveness of certain data‐layout transformations and can be a useful tool in benchmarking and automatic performance tuning. We demonstrate the effectiveness of this strategy with experiments on three multicore platforms on a workload that contains both sequential and parallel applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Early catastrophic tibial component wear after unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty is an appropriate method of treating selected patients with osteoarthritis of the medial compartment of the knee. The common causes of failure are aseptic loosening, infection, patellofemoral pain, and deterioration in the opposite compartment. Seven cases of a cohort of 32 Robert Brigham unicondylar knee replacements that failed because of early catastrophic wear of the polyethylene tibial component are reported. Possible reasons suggested for failure include inadequate thickness of polyethylene, fusion defects in the polyethylene structure as a result of the sterilization process, increased rotational freedom, and reduced conformity in the design of the prosthesis.     

Chemotaxis of Pseudomonas spp. to the polyaromatic hydrocarbon naphthalene

Two naphthalene-degrading bacteria, Pseudomonas putida G7 and Pseudomonas sp. strain NCIB 9816-4, were chemotactically attracted to naphthalene in drop assays and modified capillary assays. Growth on naphthalene or salicylate induced the chemotactic response. P. putida G7 was also chemotactic to biphenyl; other polyaromatic hydrocarbons that were tested did not appear to be chemoattractants for either Pseudomonas strain. Strains that were cured of the naphthalene degradation plasmid were not attracted to naphthalene.     

Effects of dietary corn and olive oil versus coconut fat on biliary cholesterol secretion in rats

We have studied the effects of dietary corn and olive oil versus coconut fat on bile formation and fluidity of hepatic plasma membranes in rats. After 4 weeks of feeding the purified diets containing 9% (w/w) of the test fats, there was no difference in plasma cholesterol concentration between the dietary groups. The amount of free and esterified cholesterol in the liver was significantly higher in rats fed either corn oil or olive oil as compared with coconut fat. In the rats fed olive oil, but not in those fed corn oil this was associated with lower rates of biliary phospholipid excretion. Bile flow was not differently influenced by the three dietary fats. Hepatic plasma membranes of the rats fed corn or olive oil contained more cholesterol and less phospholipids than those on coconut fat, which was, however, not accompanied by changes in fluidity of the membranes. These results indicate that in rats the type of dietary fat can induce considerable changes in hepatic cholesterol metabolism without affecting plasma cholesterol concentrations, and without consistent effects on biliary cholesterol secretion.