The ham-5, rcm-1 and rco-1 genes regulate hyphal fusion in Neurospora crassa

Mutants of Neurospora crassa unable to participate in vegetative hyphal fusion (anastomosis) were isolated and characterized. From this analysis, three genes, rcm-1, rco-1 and ham-5, were identified and shown to be required for hyphal fusion. The rcm-1 and rco-1 genes are homologues of the Saccharomyces cerevisiae SSN6 and TUP1 genes, which encode a dimeric transcription factor in yeast. We demonstrate that in N. crassa the rcm-1 and rco-1 genes are required for hyphal fusion and normal hyphal morphology, and influence both asexual and sexual development. The ham-5 gene encodes a 1686 amino acid protein with two putative WD40 domains, which might participate in protein–protein interactions. ham-5 deletion mutants had a reduced rate of hyphal extension and altered hyphal morphology, and were unable to produce the conidial anastomosis tubes that are required for hyphal fusion during colony initiation

The performance of the 30-Gallon-Drum Neutron Multiplicity Counter at Rocky Flats Environmental Technology Site

In the fall of 1994, Rocky Flats Environmental Technology Site (RFETS) committed to offering approximately one metric ton of excess weapons plutonium for safeguards verification by the International Atomic Energy Agency (IAEA). At that time RFETS decided to offer cans of plutonium of varying purity, stored one or two to a package in 10- gal. drums, and contracted with the Los Alamos to obtain a 30-Gallon- Drum Neutron Multiplicity Counter (NMC) to measure these materials. A multiplicity counter was deemed necessary because of IAEA experience that the standard coincidence counting techniques routinely used in IAEA inspections would fail for plutonium-bearing materials of variable purity. RFETS also thought that such an instrument would be useful for their domestic safeguards needs

KAUFMANN PURCELL, Susan & Françoise SIMON(dir.). Europe and Latin America in the World Economy. Boulder, Lynne Rienner Publishers, 1995, 215 p.

INTRODUCTION: Extracellular vesicles (EVs) are shed from cells and carry markers of the parent cells. Vesicles derived from cancer cells reach the bloodstream and locally influence important physiological processes. It has been previously shown that procoagulant vesicles are circulating in patients’ fluids. These EVs are therefore considered as promising biomarkers for the thrombotic risk. Because of their small size, classical methods such as flow cytometry suffer from limitation for their characterisation. Atomic force microscopy (AFM) has been proposed as a promising complementary method for the characterisation of EVs. OBJECTIVES: The objectives of this study are: (a) to develop and validate AFM with specific antibodies (anti-TF) and (b) to compare air and liquid modes for EVs’ size and number determination as potential biomarkers of the prothrombotic risk. METHODS: AFM multimode nanoscope III was used for air tapping mode (TM). AFM catalyst was used for liquid Peak Force Tapping (PFT) mode. Vesicles are generated according to Davila et al.'s protocol. Substrates are coated with various concentrations of antibodies, thanks to ethanolamine and glutaraldehyde. RESULTS: Vesicles were immobilised on antibody-coated surfaces to select tissue factor (TF)-positive vesicles. The size range of vesicles observed in liquid PFT mode is 6–10 times higher than in air mode. This corresponds to the data found in the literature. CONCLUSION: We recommend liquid PFT mode to analyse vesicles on 5 µg/ml antibody-coated substrates

Interaction of the Coronavirus Infectious Bronchitis Virus Membrane Protein with β-Actin and Its Implication in Virion Assembly and Budding

Coronavirus M protein is an essential component of virion and plays pivotal roles in virion assembly, budding and maturation. The M protein is integrated into the viral envelope with three transmembrane domains flanked by a short amino-terminal ectodomain and a large carboxy-terminal endodomain. In this study, we showed co-purification of the M protein from coronavirus infectious bronchitis virus (IBV) with actin. To understand the cellular factors that may be involved in virion assembly, budding and maturation processes, IBV M was used as the bait in a yeast two-hybrid screen, resulting in the identification of β-actin as a potentially interacting partner. This interaction was subsequently confirmed by coimmunoprecipitation and immunofluorescence microscopy in mammalian cells, and mutation of amino acids A159 and K160 on the M protein abolished the interaction. Introduction of the A159-K160 mutation into an infectious IBV clone system blocks the infectivity of the clone, although viral RNA replication and subgenomic mRNA transcription were actively detected. Disruption of actin filaments with cell-permeable agent cytochalasin D at early stages of the infection cycle led to the detection of viral protein synthesis in infected cells but not release of virus particles to the cultured media. However, the same treatment at late stages of the infection cycle did not affect the release of virus particles to the media, suggesting that disruption of the actin filaments might block virion assembly and budding, but not release of the virus particles. This study reveals an essential function of actin in the replication cycle of coronavirus

Simulation vs. Reality: A Comparison of In Silico Distance Predictions with DEER and FRET Measurements

Site specific incorporation of molecular probes such as fluorescent- and nitroxide spin-labels into biomolecules, and subsequent analysis by Förster resonance energy transfer (FRET) and double electron-electron resonance (DEER) can elucidate the distance and distance-changes between the probes. However, the probes have an intrinsic conformational flexibility due to the linker by which they are conjugated to the biomolecule. This property minimizes the influence of the label side chain on the structure of the target molecule, but complicates the direct correlation of the experimental inter-label distances with the macromolecular structure or changes thereof. Simulation methods that account for the conformational flexibility and orientation of the probe(s) can be helpful in overcoming this problem. We performed distance measurements using FRET and DEER and explored different simulation techniques to predict inter-label distances using the Rpo4/7 stalk module of the M. jannaschii RNA polymerase. This is a suitable model system because it is rigid and a high-resolution X-ray structure is available. The conformations of the fluorescent labels and nitroxide spin labels on Rpo4/7 were modeled using in vacuo molecular dynamics simulations (MD) and a stochastic Monte Carlo sampling approach. For the nitroxide probes we also performed MD simulations with explicit water and carried out a rotamer library analysis. Our results show that the Monte Carlo simulations are in better agreement with experiments than the MD simulations and the rotamer library approach results in plausible distance predictions. Because the latter is the least computationally demanding of the methods we have explored, and is readily available to many researchers, it prevails as the method of choice for the interpretation of DEER distance distributions

Local Induction of Immunosuppressive CD8+ T Cells in the Gut-Associated Lymphoid Tissues

Background: In contrast to intestinal CD4 + regulatory T cells (Tregs), the generation and function of immunomodulatory intestinal CD8 + T cells is less well defined. To dissect the immunologic mechanisms of CD8 + T cell function in the mucosa, reactivity against hemagglutinin (HA) expressed in intestinal epithelial cells of mice bearing a MHC class-I-restricted T-cellreceptor specific for HA was studied. Methodology and Principal Findings: HA-specific CD8 + T cells were isolated from gut-associated tissues and phenotypically and functionally characterized for the expression of Foxp3 + and their suppressive capacity. We demonstrate that intestinal HA expression led to peripheral induction of HA-specific CD8 + Foxp3 + T cells. Antigen-experienced CD8 + T cells in this transgenic mouse model suppressed the proliferation of CD8 + and CD4 + T cells in vitro. Gene expression analysis of suppressive HA-specific CD8 + T cells revealed a specific up-regulation of CD103, Nrp1, Tnfrsf9 and Pdcd1, molecules also expressed on CD4 + T reg subsets. Finally, gut-associated dendritic cells were able to induce HA-specific CD8 + Foxp3 + T cells. Conclusion and Significance: We demonstrate that gut specific antigen presentation is sufficient to induce CD8 + T regs in vivo which may maintain intestinal homeostasis by down-modulating effector functions of T cells