Involved in the encapsidating of the genome in a ratio of 1 N per 6 ribonucleotides, resulting in the protection from nucleases. The nucleocapsid (NC) has an helical structure with either 12.35 or 11.64 N per turn, approximately 20nm in diameter, with a hollow central cavity approximately 5nm 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.