Structural basis of Ebola virus nucleocapsid assembly and functions

The Ebola virus, a member of the Filoviridae family, causes severe hemorrhagic fever in humans. Filamentous virions contain a helical nucleocapsid responsible for genome transcription, replication, and packaging into progeny virions. The nucleocapsid consists of a helical nucleoprotein (NP)-viral genomic RNA complex forming the core structure, to which VP24 and VP35 bind externally. Two NPs, each paired with a VP24 molecule, constitute a repeating unit. However, the detailed nucleocapsid structure remains unclear. Here, we determined the nucleocapsid-like structure within virus-like particles at 4.6 Angstrom resolution using single-particle cryo-electron microscopy. Mutational analysis identified specific interactions between the two NPs and two VP24s and demonstrated that each of the two VP24s in different orientations distinctively regulates nucleocapsid assembly, viral RNA synthesis, and intracellular transport of the nucleocapsid. Our findings highlight the sophisticated mechanisms underlying the assembly and functional regulation of the nucleocapsid and provide insights into antiviral development.