Abstract
The virion glycoproteins Gn and Gc of Bunyamwera orthobunyavirus (family Bunyaviridae) are encoded by the M RNA genome segment and have roles in both viral attachment and membrane fusion. To investigate further the structure and function of the Gc protein in viral replication, we generated 12 mutants that contain truncations from the N terminus. The effects of these deletions were analysed with regard to Golgi targeting, low pH-dependent membrane fusion, infectious virus-like particle (VLP) formation and virus infectivity. Our results show that the N-terminal half (453 residues) of the Gc ectodomain (909 residues in total) is dispensable for Golgi trafficking and cell fusion. However, deletions in this region resulted in a significant reduction in VLP formation. Four mutant viruses that contained N-terminal deletions in their Gc proteins were rescued, and found to be attenuated to different degrees in BHK-21 cells. Taken together, our data indicate that the N-terminal half of the Gc ectodomain is dispensable for replication in cell culture, whereas the C-terminal half is required to mediate cell fusion. A model for the domain structure of the Gc ectodomain is proposed.
Highlights
Viruses in the family Bunyaviridae are mainly arthropod-transmitted and are classified into five genera: Orthobunyavirus, Hantavirus, Nairovirus, Phlebovirus and Tospovirus
Infection of cells by enveloped viruses is initiated by the release of the virus genome into the replication compartment through the fusion of viral and cellular membranes, a process that is mediated by the viral fusion protein(s) (Harrison, 2008; Kielian & Rey, 2006; Weissenhorn et al, 2007)
Our results revealed that the N-terminal region of the Gc ectodomain is not required for
Summary
Viruses in the family Bunyaviridae (known as bunyaviruses) are mainly arthropod-transmitted and are classified into five genera: Orthobunyavirus, Hantavirus, Nairovirus, Phlebovirus and Tospovirus. Orthobunyaviruses encode two glycoproteins called Gn and Gc that form spikes on the virus particle and are involved in viral attachment and cell fusion (Schmaljohn & Hooper, 2001) They are encoded by the medium (M) RNA genome segment as a precursor protein (Gn–NSm– Gc), which is cleaved co-translationally to yield the two mature glycoproteins and a non-structural protein termed NSm (Elliott, 1996).
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