Efficient APC/C substrate degradation in cells undergoing mitotic exit depends on K11 ubiquitin linkages.
Efficient APC/C substrate degradation in cells undergoing mitotic exit depends on K11 ubiquitin linkages.
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DOI：
10.1091/mbc.e15-02-0102
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发表时间：
2015-12-01
影响因子：
3.3
通讯作者：
Lindon C
中科院分区：
文献类型：
--
作者：
Min M;Mevissen TE;De Luca M;Komander D;Lindon C
K11 和 K48 连接的多聚泛素构成 APC/C 底物上的替代破坏信号。有丝分裂退出后期的目标底物，包括 Aurora 激酶、Polo 样激酶和 KIFC1，都依赖于 K11 连接进行降解。 APC/C 共激活因子 Cdh1 通过 UBE2S 以底物特异性方式指导 K11 连接组装。泛素蛋白酶体系统 (UPS) 通过用多泛素链对其靶标进行翻译后修饰，指导关键细胞调节因子的程序性破坏。这些通常包含 Lys-48 (K48) 定向的泛素连接，但包含非典型 Lys-11 (K11) 连接的链也以蛋白酶体为目标底物，例如调节细胞周期进程。称为后期促进复合物/环体 (APC/C) 的泛素连接酶控制有丝分裂的退出。在高等真核生物中，APC/C 与 E2 酶 UBE2S 一起在有丝分裂停滞释放的细胞中组装 K11 连接，并且这些连接被认为在有丝分裂退出期间构成改进的蛋白水解信号。我们通过将单个底物（包括 Aurora 激酶）体内 K11 特异性泛素化的定量测量与其在单细胞水平上追踪的降解动力学相关联来测试这个想法。通过该方法测试的所有后期底物均通过 UBE2S 敲低消除 K11 连接来稳定，即使相同的底物被 K48 连接的多聚泛素显着修饰。对依赖于 APC/C 共激活剂 Cdh1 降解的底物进行的具体检查显示，这些底物上的 K11 链依赖于 Cdh1 富集，而在有丝分裂退出期间添加的相同底物上的其他泛素连接则不依赖于 Cdh1。因此，我们表明 K11 连接为 APC/C 提供了一种以共激活剂指定的方式调节底物降解速率的方法。
K11- and K48-linked polyubiquitin constitute alternative destruction signals on substrates of the APC/C. Substrates targeted late in mitotic exit, including Aurora kinases, Polo-like kinase, and KIFC1, all depend on K11 linkages for degradation. APC/C coactivator Cdh1 directs K11 linkage assembly via UBE2S in a substrate-specific manner. 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.