Encapsidates the genome in a ratio of 1 N per 6 ribonucleotides, protecting it from nucleases. The nucleocapsid (NC) has a helical structure with either 12.35 or 11.64 N per turn, approximately 20 nm in diameter, with a hollow central cavity approximately 5 nm in diameter. The encapsidated genomic RNA is termed the NC and serves as template for transcription and replication. During replication, encapsidation by N is coupled to RNA synthesis and all replicative products are resistant to nucleases. N is released in the blood following lysis of measles infected cells, it interacts then with human FCGR2B on immune cells, inducing apoptosis and blocking inflammatory immune response. Ntail binds to a protein on human thymic epithelial cells, termed Nucleoprotein Receptor (NR), inducing growth arrest. Homomultimerizes to form the nucleocapsid. Binds to viral genomic RNA. In nucleocapsid, binds the P protein and thereby positions the polymerase on the template. Interacts with human FCGR2B protein. Ncore is globular and carries regions required for N self-assembly and RNA-binding. Ntail is an intrinsically disordered monomeric domain. Belongs to the paramyxoviruses nucleocapsid family. The strains used in this publication turn out to be Edmonston strain viruses, contrasting with their claimed origin from reconsituted measles virus genomic cDNAs containing a genetic tag.