The matrix protein VP40 is encoded by the third MARV gene and is the counterpart of the M proteins of other NNS RNA viruses. VP40 plays a major role in the formation of virions by redistributing nucleocapsids from the perinuclear region to the plasma membrane, recruiting GP to the sites of budding, and mediating particle release [110] [111] [112] . Overexpression of VP40 led to reduced reporter gene expression of MARV minigenomes, suggesting a regulatory role of VP40 in transcription and/or replication [113] .