Plays an essential role in the inhibition of host immune response. Prevents the establishment of cellular antiviral state by blocking interferon-alpha/beta (IFN-alpha/beta) production and signaling pathway. Interacts with host IFIH1/MDA5 and DHX58/LGP2 to inhibit the transduction pathway involved in the activation of IFN-beta promoter, thus protecting the virus against cell antiviral state. Blocks the type I and II interferon signaling pathways by interacting with host STAT1, STAT2 and STAT3, and mediating their ubiquitination and subsequent proteasomal degradation (By similarity). Interacts with host IFIH1/MDA5 and DHX58/LGP2. Forms with host DDB1, CUL4A, STAT1, STAT2 and STAT3 the mumps virus V-dependent complex (VDC) (By similarity). Partially edited. RNA editing at this position consists of an insertion of two guanine nucleotides. The sequence displayed here is the V protein, derived from the unedited RNA. The edited RNA gives rise to the P protein (AC P19717) (By similarity). Belongs to the paramyxoviruses V protein family.