English: Functional roles of the arenavirus Z protein in the viral life cycle. Regulation of viral RNA synthesis. Transcription and replication of arenaviruses takes place in the host cell cytoplasm. Z protein regulates these processes through interaction with the viral polymerase. Orchestration of viral assembly and budding. Z protein drives particle release at the plasma membrane. Through interaction with GP and viral RNPs, Z mediates their incorporation into nascent virions. Interaction with host cell proteins. Z protein interacts with several host cell factors, such as PML (promyelocytic leukemia protein), eIF4E (eukaryotic translation initiation factor 4E), PRH (proline-rich homeodomain protein), and ribosomal P proteins. The assumed biological effects of these interactions on arenavirus replication are discussed in the text. Interferon antagonism. Z proteins from various NW arenaviruses participate in IFN antagonism.While Z protein inhibits the activation of RIG-I-mediated downstream signalling pathway through direct interaction with RIG-I, NP, which is the main arenavirus interferon antagonist, causes a block in the IRF-3 activation pathway and prevents nuclear translocation of IRF-3.