TRIM21 and nasopharyngeal carcinoma: To explore whether the enrichment of cytosolic mtDNA is a critical event in TRIM21 knockout-induced enhancement of type-I IFN responses, we generated mtDNA-depleted (rho0) TRIM21-WT and TRIM21-KO NPC cells (Fig. 2e) and found that the abundance of cytosolic dsDNA (Supplementary Fig. 2g) and mtDNA (Fig. 2f) was dramatically decreased in rho0 cells either with or without TRIM21 depletion after IR treatment.