Elucidation of functional domains of Chandipura virus Nucleocapsid protein involved in oligomerization and RNA binding: implication in viral genome encapsidation.

Chandipura virus, a member of the vesiculovirus genera, has been recently recognized as an emerging human pathogen. Previously, we have shown that Chandipura virus Nucleocapsid protein N is capable of binding to both specific viral leader RNA as well as non-viral RNA sequences, albeit in distinct monomeric and oligomeric states, respectively. Here, we distinguish the regions of N involved in oligomerization and RNA binding using a panel of deletion mutants. We demonstrate that deletion in the N-terminal arm completely abrogates self-association of N protein. Monomer N specifically recognizes viral leader RNA using its C-terminal 102 residues, while oligomerization generates an additional RNA binding surface involving the N-terminal 320 amino acids of N overlapping with a protease resistant core that is capable of forming nucleocapsid like structure and also binding heterogeneous RNA sequences. Finally, we propose a model to explain the mechanism of genome encapsidation of this important human pathogen.