Domains of Rinderpest virus phosphoprotein involved in interaction with itself and the nucleocapsid protein

The yeast two-hybrid system was used to identify domains involved in specific in vivo interactions between the Rinderpest virus (RPV) phosphoprotein (P) and nucleocapsid protein (N). N and P genes were cloned in both the yeast GAL4 DNA-binding and GAL4 activation domain vectors, which enabled analysis of self and interprotein interactions. Mapping of the domain of P protein involved in its association with itself revealed that the COOH-terminal 32 amino acids (316-347) that forms a part of the highly conserved coiled coil region is important for interaction. In addition, just the coiled coil region of RPV P protein fused to the DNA-binding domain and activation domain of GAL4 was found to be sufficient to bring about activation of the beta-galactosidase reporter. Similarly, mapping of the domains of P protein involved in its interaction with N protein revealed that NH2-terminal 59 amino acids and COOH-terminal 32 amino acids (316-347) involved in P-P interaction are simultaneously required for association with N protein. Interestingly, a P protein mutant with just the NH2-terminal 59 amino acids and the coiled coil domain with all other P protein regions deleted retained its ability to interact with N protein. Furthermore, we were able to show N and P protein interaction in vitro using recombinant N and P proteins expressed in Escherichia coli, demonstrating the existence of direct physical interaction between the two proteins.