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UBE2S Drives Elongation of K11-Linked Ubiquitin Chains by the Anaphase-Promoting Complex

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The Anaphase-Promoting Complex (APC) is an E3 ubiquitin ligase that regulates mitosis and G1 by sequentially targeting cell-cycle regulators for ubiquitination and proteasomal degradation. The mechanism of ubiquitin chain formation by APC and the resultant chain topology remains controversial. By using a single-lysine APC substrate to dissect the topology of ubiquitinated substrates, we find that APC-catalyzed ubiquitination has an intrinsic preference for the K11 linkage of ubiquitin that is essential for substrate degradation. K11 specificity is determined by an E2 enzyme, UBE2S/E2-EPF, that elongates ubiquitin chains after the substrates are pre-ubiquitinated by UbcH10 or UbcH5. UBE2S copurifies with APC; dominant-negative Ube2S slows down APC substrate degradation in functional cell-cycle extracts. We propose that Ube2S is a critical, unique component of the APC ubiquitination pathway.
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... Lys11-linked ubiquitin chains may be of particular interest as a research direction for PROTAC developers, since they have proven to be critical regulators of mitotic protein degradation through the proteasome [76]. Their formation and destruction require the recruitment of a specific set of anaphase-promoting complex (APC/C), its specific chain-elongating E2, Ube2S and deubiquitinase [71,77,78], although it was shown that homotypic Lys11 chains did not bind to pure proteasomes or proteasomeassociated ubiquitin receptors [79]. ...
... Hydrolysis of such chains can be carried out by several enzymes, among which OTULIN is specific for this type of conjugation [52,118,120,121]. Similarly, Lys11 linked chains require linkage-specific enzymes: the anaphase-promoting complex (APC/C) and its specific chain-elongating E2, Ube2S; for cleavage -the Lys11 specific Cezanne [77,[122][123][124]. The role of such ubiquitinylation increases during cell division, when these conjugates target cell cycle regulators [122,125]. ...
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... The APC/C and its E2s can perform a vast number of different ubiquitination reactions [21][22][23][29][30][31][32][33][34]41 . Trapping each of these individual structural states has required detailed biochemical knowledge about the system to stabilize the reaction intermediates 23,27,[36][37][38]42 . ...
... UBE2C can either continue to modify substrate lysines or make short chains 21,[29][30][31] . A second E2, UBE2S, extends the K11-linked Ub chains on the substrate [32][33][34] . These reactions can all occur during a single substrate-binding event while the E2s require multiple rounds of transient binding and catalysis to modify the substrate. ...
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... E2 enzymes play a crucial role in determining the linkage specificity of the polyubiquitin chain (19)(20)(21). For instance, the human E2s Ube2C/UbcH10 and Ube2S (15,22) and the Arabidopsis homolog UBC22 (23) are able to catalyze K11-linked ubiquitination. An in vitro ubiquitination assay showed that AtUBC10 can conjugate both K48 and K63 linkages, while AtUBC35 mostly prefers K63 sites (24). ...
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... 10 UBE2S, a K11 linkage-specific E2, can prolong K11-linked polyubiquitin chains on substrates through cooperation with Ube2c/d or anaphase-promoting complex/cyclosome (APC/C). [11][12][13] Moreover, UBE2S can regulate differentiation of Sox2-mediated embryonic stem cell and associate with Ku70 for DNA repair. 14 Recently, many studies have indicated that UBE2S is overexpressed in multiple human primary cancers and is involved in tumorigenesis. ...
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