TRIM21 and colorectal carcinoma: We found that the mutations of all lysines in the KR-1 group, but not those in other groups, completely abolished the TRIM21-mediated POU2F1 degradation, suggesting that lysines (K272, 293 and 296) in this region of POU2F1 may be critical for the TRIM21-mediated POU2F1 ubiquitination in CRC cells (Figure 6J).