Plays a crucial role in virion assembly and budding. Expressed late in the virus life cycle, it acts as an inhibitor of viral transcription and RNA synthesis by interacting with the viral polymerase L. Presumably recruits the NP encapsidated genome to cellular membranes at budding sites via direct interaction with NP. Plays critical roles in the final steps of viral release by interacting with host TSG101, a member of the vacuolar protein-sorting pathway and using other cellular host proteins involved in vesicle formation pathway. The budding of the virus progeny occurs after association of protein Z with the viral glycoprotein complex SSP-GP1-GP2 at the cell periphery, step that requires myristoylation of protein Z. Also selectively represses protein production by associating with host eIF4E. Interacts with protein NP; this interaction probably directs the encapsidated genome to budding sites (By similarity). Interacts (via RING domain) with polymerase L; this interaction inhibits viral transcription and replication (By similarity). Interacts with the glycoprotein complex; this interaction plays a role in virion budding. Interacts with host eIF4E; this interaction results in eIF4E reduced affinity for its substrate, the 5'-m7 G cap structure. Interacts (via late-budding domain) with host TSG101; this interaction is essential for budding and release of viral particles. Interacts with host RPLP0; this interaction may serve to load ribosome-like particles inside the virion. Interacts with host PML; this interaction induces PML bodies redistribution in the cytoplasm upon viral infection. Mainly perinuclear. During budding, associates at the inner side of the plasma membrane of infected cells. Late-budding domains (L domains) are short sequence motifs essential for viral particle budding. They recruit proteins of the host ESCRT machinery (Endosomal Sorting Complex Required for Transport) or ESCRT-associated proteins. Belongs to the arenaviridae Z protein family.