TRIM21 and viral infectious disease: During viral infections, the IFN/JAK/signal transducer and activator of the transcription (STAT) signaling pathway activates TRIM21 (Tripartite Motif Containing 21), a cytosolic ubiquitin ligase, which catalyzes the polyubiquitination of MAVS, a crucial biochemical step to promote TBK1 recruitment to MAVS [127].