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PLoS One. 2012;7(4):e34623. doi: 10.1371/journal.pone.0034623. Epub 2012 Apr 2.

Interaction of chandipura virus N and P proteins: identification of two mutually exclusive domains of N involved in interaction with P.

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Department of Biotechnology and Dr BC Guha Centre for Genetic Engineering and Biotechnology, University of Calcutta, Kolkata, West Bengal, India.


The nucleocapsid protein (N) and the phosphoprotein (P) of nonsegmented negative-strand (NNS) RNA viruses interact with each other to accomplish two crucial events necessary for the viral replication cycle. First, the P protein binds to the aggregation prone nascent N molecules maintaining them in a soluble monomeric (N(0)) form (N(0)-P complex). It is this form that is competent for specific encapsidation of the viral genome. Second, the P protein binds to oligomeric N in the nucleoprotein complex (N-RNA-P complex), and thereby facilitates the recruitment of the viral polymerase (L) onto its template. All previous attempts to study these complexes relied on co-expression of the two proteins in diverse systems. In this study, we have characterised these different modes of N-P interaction in detail and for the first time have been able to reconstitute these complexes individually in vitro in the chandipura virus (CHPV), a human pathogenic NNS RNA virus. Using a battery of truncated mutants of the N protein, we have been able to identify two mutually exclusive domains of N involved in differential interaction with the P protein. An unique N-terminal binding site, comprising of amino acids (aa) 1-180 form the N(0)-P interacting region, whereas, C-terminal residues spanning aa 320-390 is instrumental in N-RNA-P interactions. Significantly, the ex-vivo data also supports these observations. Based on these results, we suggest that the P protein acts as N-specific chaperone and thereby partially masking the N-N self-association region, which leads to the specific recognition of viral genome RNA by N(0).

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