The Borna disease virus (BDV) nucleoprotein (N) monomer resembles the nucleoprotein structures from rabies virus (RABV) and vesicular stomatitis virus (VSV). We show that BDV N assembles into ring- and string-like structures in the presence of 5' genomic BDV RNA. RNA induced polymerization is partly RNA-specific since polymerization is inefficient in the presence of 3' genomic BDV RNA or E. coli RNA. Mutagenesis of basic residues located in the cleft made up by the N- and C-terminal domains of N abrogate RNA-induced polymerization indicating that BDV N binds RNA similarly as observed in case of RABV and VSV N-RNA complexes. Bound RNA is not protected and sensitive to degradation. N-RNA polymers form complexes with the phosphoprotein P as required for functional transcription or replication units. Our data indicate that BDV N utilizes similar structural principles for N-RNA and N-P-RNA complex formation as observed for related negative strand RNA viruses.
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