Nucleoprotein (NP) binds to the viral RNA genomic segments in a sequence-independent manner to form ribonucleoprotein complexes and protect the viral genome from degradation. The protein contains nuclear localization signals to allow for the import of the viral genome into the host nucleus. Due to its size, NP is not translocated into the nucleus. Although NP lacks enzymatic activity, it is also involved in transcription as an elongation factor for viral RNA polymerase and viral replication through recruitment to ribonucleoprotein complexes. Interactions with polymerase basic proteins 1 and 2 have been demonstrated. During later stages of infection, NP is involved in viral packaging. Matrix protein 1 (M1) may interact with NP to hide the nuclear localization signal and thus allow the formation of viral particles. Upon a new infection, M1 dissociates from NP due to the acidification of the viral particle caused by matrix protein 2 (proton channel).