Mediates the regulatory switch from transcription to RNA replication (By similarity). Acts late in infection by inhibiting viral transcription and up-regulating RNA replication (By similarity). Plays a major role in antagonizing the type I IFN-mediated antiviral response (PubMed:23015697). Interacts with host MAVS and prevents the interaction with its upstream partner DDX58/RIG-I in the signaling pathway leading to interferon production (PubMed:23015697). Interacts with host MAVS; this interaction inhibits signaling pathway leading to interferon production. Belongs to the metapneumovirus M2-2 protein family.