MAVS and viral infectious disease: Moreover, SZ19-ΔF2 virus infection specifically enhanced the K27-linked, but not K48- or K63-linked endogenous ubiquitination of MAVS, in contrast, knockdown of PB1 inhibited the SZ19-ΔF2-induced K27-linked, but not K48- or K63-linked endogenous ubiquitination of MAVS (Fig 5D).