To identify which lysine(s) in POU2F1 is required for TRIM21-mediated POU2F1 ubiquitination and subsequent degradation, we firstly constructed different structural domains of POU2F1 mutants (Figure 6F), and the results revealed that the region (176-351aa) of POU2F1 was essential for the TRIM21-mediated POU2F1 ubiquitination in CRC cells (Figure 6G-H). This evidence concerns the gene TRIM21 and colorectal carcinoma.