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Chracterization of the molecular features of the pestivirus Erns protein with regard to its function as structural component of the virion and virulence factor (2. Funding period)
Project
Project code: FLI-IfI-08-Ri-0643
Contract period: 01.06.2018
- 31.05.2020
Purpose of research: Basic research
Keywords: viruses, pestviruses, Erns protein
The Erns protein of pestiviruses represents a specifically interesting viral protein since it combines the role of a structural surface protein with functions in repression of the type 1 interferon response, establishment of persistent infection and virulence in the natural host with the latter three features linked to the RNase activity of this protein. The mechanisms underlying both functions of the protein are not known in detail and will be investigated in the planned studies. Major questions in context with the function as a structural protein concern the role of Erns in virion assembly and budding and identification of the structure responsible for sorting of the protein into the virus particle. A special focus of the work will be on the importance of the unusual Erns membrane anchor with its conserved amino acid motifs for these processes. The virulence factor function of Erns is so far regarded to depend on its intrinsic RNase activity, its dimerization and its partial secretion form the host cell. The planned work aims at elucidation of the biochemical and cell biological basis of these features of Erns. The results of this work will contribute to understanding general aspects of pestivirus biology and the interaction of these viruses with the immune system of their hosts.
Mutation analyses revealed that conserved features of the Erns membrane anchor, especially the distribution of charged amino acids, is highly important for Erns processing, secretion and homodimer formation. Replacement of single charged residues significantly influenced pestivirus replication. We detected reversions or pseudoreversions (replacement by an alternative amino acid with identical charge as the original one) in viruses recovered from mutated sequences. Other exchanges were conserved during RNA replication but prevented the generation of infectious virus particles. The defect of these mutants could be shown to rely on assembly and/or release of virus particles. Surprisingly, our experiments revealed that Erns is not secreted as a soluble protein as hypothesized so far, but bound to lipid vesicles. Mutations introduced into the Erns membrane anchor were able to increase the secretion of vesicle bound Erns. Our results help to elucidate how Erns acts both as structural protein and secreted virulence factor. We show that the Erns membrane anchor is the key structure that links both functions of this protein.
Section overview
Subjects
- Animal health
- Biotechnology
