Encapsidates the genome, protecting it from nucleases. The encapsidated genomic RNA is termed the nucleocapsid (NC). Serves as template for viral transcription and replication. The increased presence of protein N in host cell does not seem to trigger the switch from transcription to replication as observed in other negative strain RNA viruses. Through the interaction with host IKBKE, strongly inhibits the phosphorylation and nuclear translocation of host IRF3, a protein involved in interferon activation pathway, leading to the inhibition of interferon-beta and IRF3-dependent promoters activation. Encodes also a functional 3'-5' exoribonuclease that degrades preferentially dsRNA substrates and thereby participates in the suppression of interferon induction. Homomultimerizes to form the nucleocapsid. Binds to viral genomic RNA. Interacts with glycoprotein G2. Interacts with protein Z; this interaction probably directs the encapsidated genome to budding sites. Interacts with protein L; this interaction does not interfere with Z-L interaction. Interacts with host IKBKE (via Protein kinase domain); the interaction inhibits IKBKE kinase activity (PubMed:22532683). The N-terminal region is important for the cap-binding activity while the C-terminal region contains the 3'-5' exoribonuclease activity. A CCHE zinc binding site is present in the C-terminal region and may thus contribute to the substrate binding and/or the specificity of the exonuclease activity. Belongs to the arenaviridae nucleocapsid protein family.