Domains of the Measles Virus N Protein Required for Binding to P Protein and Self-Assembly

AbstractThe nucleocapsid protein (N, 525 amino acids) of measles virus plays a central role in the replication of the viral genomic RNA. Its functions require interactions with itself and with other viral components. The N protein encapsidates genomic RNA, a function reflected in its ability to self-assemble into nucleocapsid-like particles in the absence of other viral proteins. The substrate for the packaging of nascent RNA during RNA replication is a complex between the N and phosphoprotein (P). The domains on the N protein that promote binding to P protein and self-assembly have been identified utilizing a series of N protein deletions. Two noncontiguous regions, amino acids 4–188 and 304–373 of N protein, are required for the formation of the soluble N–P complex, while deletion of amino acids 189–239 did not affect N–P binding. Amino acids 240–303 appear to be necessary for the stability of the protein. The N-terminal 398 amino acids are all required for the formation of organized nucleocapsid-like particles, since deletion of the central region from amino acids 189–373 completely abolished N–N interaction, and deletion of amino acids 4–188 and 374–492 caused the formation of unstructured aggregates