Efficient APC/C substrate degradation in cells undergoing mitotic exit depends on K11 ubiquitin linkages.

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Min, Mingwei 
Mevissen, Tycho ET 
De Luca, Maria 
Komander, David 
Lindon, Catherine 

The ubiquitin proteasome system (UPS) directs programmed destruction of key cellular regulators via posttranslational modification of its targets with polyubiquitin chains. These commonly contain Lys-48 (K48)-directed ubiquitin linkages, but chains containing atypical Lys-11 (K11) linkages also target substrates to the proteasome--for example, to regulate cell cycle progression. The ubiquitin ligase called the anaphase-promoting complex/cyclosome (APC/C) controls mitotic exit. In higher eukaryotes, the APC/C works with the E2 enzyme UBE2S to assemble K11 linkages in cells released from mitotic arrest, and these are proposed to constitute an improved proteolytic signal during exit from mitosis. We tested this idea by correlating quantitative measures of in vivo K11-specific ubiquitination of individual substrates, including Aurora kinases, with their degradation kinetics tracked at the single-cell level. All anaphase substrates tested by this methodology are stabilized by depletion of K11 linkages via UBE2S knockdown, even if the same substrates are significantly modified with K48-linked polyubiquitin. Specific examination of substrates depending on the APC/C coactivator Cdh1 for their degradation revealed Cdh1-dependent enrichment of K11 chains on these substrates, whereas other ubiquitin linkages on the same substrates added during mitotic exit were Cdh1-independent. Therefore we show that K11 linkages provide the APC/C with a means to regulate the rate of substrate degradation in a coactivator-specified manner.

Anaphase, Anaphase-Promoting Complex-Cyclosome, Aurora Kinases, Cell Cycle, Cell Line, Tumor, HeLa Cells, Humans, Lysine, Proteasome Endopeptidase Complex, Protein Processing, Post-Translational, Proteolysis, Ubiquitin, Ubiquitin-Conjugating Enzymes, Ubiquitination
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Mol Biol Cell
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American Society for Cell Biology (ASCB)
Medical Research Council (G120/892)
Medical Research Council (MR/M01102X/1)
Cancer Research Uk (None)
Work in CL lab was funded by Medical Research Council [G120/892], Cancer Research UK [C3/A10239] and the Department of Genetics. Work in DK lab is funded by Medical Research Council [U105192732], European Research Council [309756], and the Lister Institute for Preventive Medicine. MM was supported by Great Britain China Centre Educational Trust and the Henry Lester Trust. TM is funded by Marie Curie Initial Training Network “UPStream”.