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. 2000 May;2(3):208–225. doi: 10.1038/sj.neo.7900073

Figure 2.

Figure 2

Ubiquitin-dependent proteolysis of p53. In a sequential enzymatic reaction (E1–E3), ubiquitin (Ub) is activated and added onto the p53 protein. The ubiquitylated p53 protein is than targeted for proteolysis by the 26S proteasome. The proteins involved in directing ubiquitylation of p53 are the cellular proteins, MDM2 and JNK. The HPV 16 protein E6 can also target p53 for degradation by acting as a ubiquitin ligase. Following cellular stresses, proteasome-mediated degradation of p53 is stopped. The p53 protein can also accumulate by default following inhibition of proteasome activity with certain drugs.