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. 2018 Jan 3;4(1):e1701393. doi: 10.1126/sciadv.1701393

Fig. 4. xUB transfer through the OUT cascade of E4B and CHIP to p53.

Fig. 4

(A) fE4B-KB2 and fE4B-KB12 could assemble an OUT cascade with xUba1 and xUbcH5b to mediate xUB transfer to p53. The efficiency of p53 ubiquitination by xUB and the OUT cascade was similar to p53 ubiquitination with wt UB and the wt Uba1-UbcH5b-fE4B cascade. In contrast, wt E4B could not pair with xUba1-xUbcH5b to transfer xUB to p53, suggesting the orthogonality between the OUT cascade and native E3s. Mutant fE4B KB2 or KB12 could not pair with wt Uba1–wt UbcH5b to transfer wt UB to p53. (B) Similar to E4B OUT cascade, CHIP-KB2 and CHIP-KB12 could relay with xUba1-xUbcH5b to transfer xUB to p53. The efficiency of xUB modification of p53 by the CHIP OUT cascades was similar to that of p53 modification by wt UB going through the wt Uba1-UbcH5b-CHIP cascade. xUB could not be transferred to p53 with the crossover cascade of xUba1-xUbcH5b–wt CHIP. wt UB could not be transferred to p53 with the crossover cascade of wt Uba1–wt UbcH5b–mutant CHIP (KB2 or KB12).