Mapping the domains on the phosphoprotein of bovine respiratory syncytial virus required for N–P interaction using a two-hybrid system

Specific interactions between the nucleocapsid protein (N) and the phosphoprotein (P) of bovine respiratory syncytial virus (BRSV) have been investigated using a yeast-based two-hybrid system. Plasmids encoding the yeast GAL4 DNA binding domain fused with the N gene and GAL4 activation domain fused with the P gene were cotransfected into competent yeast cells. The ability of the N and P proteins to interact in vivo was measured by activation of the lacZ reporter gene by the GAL4 transactivation region. Results indicated that the N and P proteins interact very strongly in vivo. When interactions between N and various deletion mutants of the P protein were examined, an internal region (aa 132–168) and the highly acidic C-terminal region (aa 236–241) of the P protein were found to be essential for N-P interaction. In addition, the highly basic N-terminal region (amino acids 1–40) was found to be involved in N-P interaction to a lesser extent.