title: The respiratory syncytial virus fusion protein targets to the perimeter of inclusion bodies and facilitates filament formation by a cytoplasmic tail-dependent mechanism.
abstract: The human respiratory syncytial virus (HRSV) fusion (F) protein cytoplasmic tail (CT) and matrix (M) protein are key mediators of viral assembly, but the underlying mechanisms are poorly understood. A complementation assay was developed to systematically examine the role of the F protein CT in infectious virus production. The ability of F mutants with alanine substitutions in the CT to complement an F-null virus in generating infectious progeny was quantitated by flow cytometry. Two CT regions with impact on infectious progeny production were identified: residues 557 to 566 (CT-R1) and 569 to 572 (CT-R2). Substitutions in CT-R1 decreased infectivity by 40 to 85% and increased the level of F-induced cell-cell fusion but had little impact on assembly of viral surface filaments, which are believed to be virions. Substitutions in CT-R2, as well as deletion of the entire CT, abrogated infectious progeny production and impaired viral filament formation. However, CT-R2 mutations did not block but rather delayed the formation of viral filaments, which continued to form at a low rate and contained the viral M protein and nucleoprotein (N). Microscopy analysis revealed that substitutions in CT-R2 but not CT-R1 led to accumulation of M and F proteins within and at the perimeter of viral inclusion bodies (IBs), respectively. The accumulation of M and F at IBs and coincident strong decrease in filament formation and infectivity upon CT-R2 mutations suggest that F interaction with IBs is an important step in the virion assembly process and that CT residues 569 to 572 act to facilitate release of M-ribonucleoprotein complexes from IBs.
authors.affiliation: Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, Oklahoma, USA.
authors.forename: Pradyumna S
authors.initials: PS
authors.lastname: Baviskar
authors.forename: Anne L
authors.initials: AL
authors.lastname: Hotard
authors.forename: Martin L
authors.initials: ML
authors.lastname: Moore
authors.forename: Antonius G P
authors.initials: AG
authors.lastname: Oomens
mesh_terms: D000818:Animals; D002459:Cell Fusion; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000821:virology*; D005434:Flow Cytometry; D006801:Humans; D007181:Inclusion Bodies, Viral / Q000378:metabolism*; D008561:Membrane Fusion; D009154:Mutation / Q000235:genetics; D018357:Respiratory Syncytial Virus Infections / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D018113:Respiratory Syncytial Virus, Human / Q000472:pathogenicity*; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C526850:F protein, human respiratory syncytial virus; D014760:Viral Fusion Proteins; D014763:Viral Matrix Proteins
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