Coordinated interactions among Nipah virus N, P and M proteins drive formation of distinct inclusion bodies

Nipah virus (NiV), a highly pathogenic zoonotic paramyxovirus, forms two distinct types of membrane-less organelles called inclusion bodies (IBs): cytosolic IBs, which serve as sites of viral RNA synthesis, and those beneath the plasma membrane (IB-PMs), which function in viral particle assembly and budding. We identified the essential domains of the NiV nucleocapsid (N) and phospho (P) proteins required for the formation of cytosolic IB-like structures with liquid-like properties. Dual-site interactions between the N- and C-terminal regions of the N and P proteins were necessary for generating these liquid organelles. In contrast, the matrix protein, along with the N and P proteins, was indispensable for the formation of IB-PM-like structures with low internal fluidity. These findings demonstrate that NiV employs specific protein-protein interactions to generate spatially and functionally distinct IBs, providing new insight into the molecular mechanisms governing viral RNA synthesis and particle formation.