Measles virus possesses a non segmented, single stranded, negative sense RNA genome that is encapsidated by the nucleoprotein to form a helical nucleocapsid. This ribonucleoproteic complex is the substrate for both transcription and replication. The RNA-dependent RNA polymerase binds to the nucleocapsid template via its co-factor, the phosphoprotein. This book focuses on the main structural information available on the nucleoprotein, showing that it consists of a structured core (NCORE) and of an intrinsically disordered C-terminal domain (NTAIL). The functional implications of the disordered...