Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 2010 Jan 26;107(4):1355-60. doi: 10.1073/pnas.0912802107. Epub 2010 Jan 6.
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.
后期促进复合物(APC)是一种 E3 泛素连接酶,通过顺序靶向细胞周期调节剂进行泛素化和蛋白酶体降解来调节有丝分裂和 G1。APC 形成泛素链的机制和由此产生的链拓扑结构仍然存在争议。通过使用单个赖氨酸 APC 底物来剖析泛素化底物的拓扑结构,我们发现 APC 催化的泛素化对泛素 K11 连接具有内在偏好,这对于底物降解至关重要。K11 特异性由 E2 酶 UBE2S/E2-EPF 决定,该酶在 UbcH10 或 UbcH5 预先泛素化底物后延长泛素链。UBE2S 与 APC 共纯化;显性负性 Ube2S 会在功能性细胞周期提取物中减缓 APC 底物的降解。我们提出 Ube2S 是 APC 泛素化途径的关键独特组成部分。