Rous Sarcoma Virus Expression in <i>Saccharomyces cerevisiae</i>: Processing and Membrane Targeting of the <i>gag</i> Gene Product

In avian cells, the product of the gag gene of Rous sarcoma virus, Pr76gag, has been shown to be targeted to the plasma membrane, to form virus particles, and then to be processed into mature viral gag proteins. To explore how these phenomena may be dependent upon cellular (host) factors, we expressed the Rous sarcoma virus gag gene in a lower eucaryote, Saccharomyces cerevisiae, and studied the behavior of the gag gene product. We show here that Pr76gag is processed in yeast cells and that this processing is specific, since it is abolished in a mutant in which the active site of the gag protease has been destroyed. In this mutant, the uncleaved precursor is found associated with the yeast plasma membrane, yet no virus particles were detected in cells or in the culture medium. From our results, we can speculate either that in yeast cells, a host protease initiates Pr76gag processing in the cytosol or that in avian cells, an inhibitor prevents the processing until the viral particle is formed

Association of Three Chicken Proteins with the 34 kD Target of Rous Sarcoma Virus Tyrosine Kinase

Transformation of chicken embryo fibroblasts by avian retroviruses induces the tyrosine phosphorylation of a 34–39 kD cellular protein (p34). In vitro, p34 isolated from intestine interacts with F-actin in a Ca²⁺-dependent manner. We report here that, in the absence of Ca²⁺ chelators, three proteins co-purified with p34 extracted from a cytosolic or membrane fraction of chicken embryo fibroblasts; these two fractions account respectively for 10–20% and 50% of the total cellular p34. Isolated from the cytosoluble fraction of fibroblasts by sucrose gradient centrifugation and hydrophobic chromatography, p34 and the other proteins behaved as a homogeneous species upon non-denaturing gel electrophoresis, gel filtration, and CsCl density gradient centrifugation, thus indicating a strong association. Moreover, an analysis by electron microscopy following uranyl acetate staining revealed particles with a raspberry-like shape. This association was always disrupted by the calcium-chelating agent, EGTA

A cellular protein phosphorylated by the avian sarcoma virus transforming gene product is associated with ribonucleoprotein particles

In chick embryo fibroblasts transformed by Rous sarcoma virus (RSV) the tyrosine phosphorylation of a cellular protein of 34,000 daltons mol. wt. (34 kd) is greatly enhanced; this was shown to be catalyzed by the phosphotransferase activity of RSV transforming protein pp60src. We report here that in cytoplasmic extracts of both normal and transformed cells, in the presence of magnesium ions, the majority of the 34‐kd protein is associated with large structures and that a fraction of 34 kd appears to be associated with ribonucleoprotein particles (RNPs). In addition, upon u.v. light cross‐linking of RNA to protein in normal or transformed cells, an anti‐34 kd serum immunoprecipitates RNA fragments of apparent low sequence complexity as detected by T1 fingerprint analysis. Our results indicate that the 34‐kd protein may play a role in the cell at the level of RNPs

A 20S Particle Ubiquitous from Yeast to Human

We have purified and characterized a particle sedimenting at 20S from the postribosomal fraction of yeast, wheat germ,Drosophila melanogaster tissue culture cells, chicken embryo fibroblasts, rabbit reticulocyte lysate, and HeLa cells. Most of the protein constituents of the 20S particle have molecular weights of 20–35 kd and differ between species; however, some do have similar molecular weights and isoelectric points, suggesting they are related. Several low-molecular-weight RNAs, distinct from tRNAs, co-purify with the particle isolated from all these species and show increasingly more complex patterns ascending the arbitrary order from yeast to human (yeast, plant, insect, bird, and mammals). InDrosophila, we present evidence that these small RNAs are tightly associated with this 20S structure

Corrective surgery for idiopathic scoliosis after heart transplantation

Cardiac transplant surgery is being performed with increasing frequency as a treatment for end-stage heart disease. In addition to the well-known post-surgical problems of rejection and infection, these patients may present at a future date with other medical problems which require surgical treatment, including orthopaedic pathology. Severe idiopathic scoliosis has been described in association with congenital heart disease, and its surgical treatment poses considerable risks because of heart disease. Spinal fusion in heart transplant recipients involves similar risks due to the particular physiology and pharmacological reactions of the denervated heart. Several cases of cholecystectomy performed in heart transplant recipients have been described, but to our knowledge no orthopaedic procedures have been reported in such patients. We report on a 15-year-old patient who underwent successful corrective surgery for idiopathic scoliosis 14 months after heart transplant

Emergency service staff and social media – A comparative empirical study of the attitude by Emergency Services staff in Europe in 2014 and 2017

Finding a way to ensure an effective use of social media has become increasingly important to emergency services over the past decade. Despite all efforts to determine the utility of social media for emergency organisations, it is necessary to benefit from such institutions' staffs' opinions to establish effective use. To provide empirical evidence we present a comparison of two surveys, conducted across Europe with emergency services in 2014 and 2017 respectively, with a total of 1169 answers. The analysis shows that personal experience has an effect on how organisational usage of social media is perceived and how emergency service staff view the future use of social media. Furthermore, the use has increased. This article not only shows emergency services what their staff think about their social media usage but also discusses challenges and future directions for the design of systems that can be useful for further development of optimized organisational social media usage