Examinando por Autor "Tischler, Nicole D."

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    Acidification triggers Andes hantavirus membrane fusion and rearrangement of Gc into a stable post-fusion homotrimer
    (Microbiology Society, 2015-11) Acuña, Rodrigo; Bignon, Eduardo A.; Mancini, Roberta; Lozach, Pierre-Yves; Tischler, Nicole D.
    The hantavirus membrane fusion process is mediated by the Gc envelope glycoprotein from within endosomes. However, little is known about the specific mechanism that triggers Gc fusion activation, and its pre- and post-fusion conformations. We established cell-free in vitro systems to characterize hantavirus fusion activation. Low pH was sufficient to trigger the interaction of virus-like particles with liposomes. This interaction was dependent on a pre-fusion glycoprotein arrangement. Further, low pH induced Gc multimerization changes leading to non-reversible Gc homotrimers. These trimers were resistant to detergent, heat and protease digestion, suggesting characteristics of a stable post-fusion structure. No acid-dependent oligomerization rearrangement was detected for the trypsin-sensitive Gn envelope glycoprotein. Finally, acidification induced fusion of glycoprotein-expressing effector cells with non-susceptible CHO cells. Together, the data provide novel information on the Gc fusion trigger and its non-reversible activation involving lipid interaction, multimerization changes and membrane fusion which ultimately allow hantavirus entry into cells. © 2015 The Authors.
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    Complete sequence of the genome of the human isolate of Andes virus CHI-7913: comparative sequence and protein structure analysis
    (Sociedad de Biología de Chile, 2003) Tischler, Nicole D.; Fernández, Jorge; Müller, Ilse; Martínez, Rodrigo; Galeno, Héctor; Villagra, Eliecer; Mora, Judith; Ramírez, Eugenio; Rosemblatt, Mario; Valenzuela, Pablo D.T.
    We report here the complete genomic sequence of the Chilean human isolate of Andes virus CHI-7913. The S, M, and L genome segment sequences of this isolate are 1,802, 3,641 and 6,466 bases in length, with an overall GC content of 38.7%. These genome segments code for a nucleocapsid protein of 428 amino acids, a glycoprotein precursor protein of 1,138 amino acids and a RNA-dependent RNA polymerase of 2,152 amino acids. In addition, the genome also has other ORFs coding for putative proteins of 34 to 103 amino acids. The encoded proteins have greater than 98% overall similarity with the proteins of Andes virus isolates AH-1 and Chile R123. Among other sequenced Hantavirus, CHI-7913 is more closely related to Sin Nombre virus, with an overall protein similarity of 92%. The characteristics of the encoded proteins of this isolate, such as hydrophobic domains, glycosylation sites, and conserved amino acid motifs shared with other Hantavirus and other members of the Bunyaviridae family, are identified and discussed.
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    Hantavirus Gc glycoprotein: Evidence for a class ll fusion protein
    (Microbiology Society, 2005-11) Tischler, Nicole D.; Gonzales, Angel; Perez-Acle, Tomas; Rosemblatt, Mario; Valenzuela, Pablo D.T.
    Hantavirus cell entry is promoted by its envelope glycoproteins, Gn and Gc, through cell attachment and by fusion between viral and endosomal membranes at low pH. However, the role of Gn and Gc in receptor binding and cell fusion has not yet been defined. In this work, a sequence presenting characteristics similar to those of class II fusion peptides (FPs) of alphavirus E1 and flavivirus E proteins is identified within the hantavirus Gc glycoprotein. A three-dimensional comparative molecular model based on crystallographic data of tick-borne encephalitis virus E protein is proposed for the Andes virus (ANDV) Gc ectodomain, which supports a feasible class II fusion-protein fold. In vitro experimental evidence is provided for the binding activity of the ANDV FP candidate to artificial membranes, as demonstrated by fluorescence anisotropy assays. Taken together, these results support the hypothesis that the Gc glycoprotein of hantaviruses and of other members of the family Bunyaviridae directs the viral fusion activity and that it may be classified as a class II viral fusion protein. © 2005 SGM.