Role of the UBL-UBA protein KPC2 in degradation of p27 at G1 phase of the cell cycle
Role of the UBL-UBA protein KPC2 in degradation of p27 at G1 phase of the cell cycle
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DOI：
10.1128/mcb.25.21.9292-9303.2005
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发表时间：
2005-11-01
影响因子：
5.3
通讯作者：
Nakayama, KI
中科院分区：
文献类型：
--
作者：
Hara, T;Kamura, T;Nakayama, KI
KPC 2（Kip 1泛素化促进复合物2）与KPC 1一起形成泛素连接酶KPC，其调节细胞周期蛋白依赖性激酶抑制剂p27在细胞周期的G1期的降解。KPC 2含有一个泛素样（UBL）结构域、两个泛素相关（乌巴）结构域和一个热休克伴侣蛋白结合（STI 1）结构域。我们现在发现KPC 2通过其UBL结构域与KPC 1相互作用，通过其UBL和NH 2-末端乌巴结构域与26 S蛋白酶体相互作用，通过其乌巴结构域与多泛素化蛋白相互作用。发现KPC 2与KPC 1的结合以依赖于KPC 2的STI 1结构域的方式稳定KPC 1。缺乏NH 2-末端或COOH-末端乌巴结构域的KPC 2突变体支持p27在体外的多泛素化，而缺乏STI 1结构域的KPC 2衍生物在这方面受到极大损害。通过RNA干扰耗尽KPC 2导致抑制p27在G1期的降解，并且将KPC 2衍生物引入KPC 2耗尽的细胞中揭示了KPC 2的NH 2-末端乌巴结构域对于p27降解是必需的。这些观察结果表明，KPC 2与KPC 1协同调节p27降解，并且KPC 2的STI 1结构域以及UBL和乌巴结构域对其功能是必不可少的。
KPC2 (Kip1 ubiquitylation-promoting complex 2) together with KPC1 forms the ubiquitin ligase KPC, which regulates degradation of the cyclin-dependent kinase inhibitor p27 at the G, phase of the cell cycle. KPC2 contains a ubiquitin-like (UBL) domain, two ubiquitin-associated (UBA) domains, and a heat shock chaperonin-binding (STI1) domain. We now show that KPC2 interacts with KPC1 through its UBL domain, with the 26S proteasome through its UBL and NH2-terminal UBA domains, and with polyubiquitylated proteins through its UBA domains. The association of KPC2 with KPC1 was found to stabilize KPC1 in a manner dependent on the STI1 domain of KPC2. KPC2 mutants that lacked either the NH2-terminal or the COOH-terminal UBA domain supported the polyubiquitylation of p27 in vitro, whereas a KPC2 derivative lacking the STI1 domain was greatly impaired in this regard. Depletion of KPC2 by RNA interference resulted in inhibition of p27 degradation at the G, phase, and introduction of KPC2 derivatives into the KPC2-depleted cells revealed that the NH2-terminal UBA domain of KPC2 is essential for p27 degradation. These observations suggest that KPC2 cooperatively regulates p27 degradation with KPC1 and that the STI1 domain as well as the UBL and UBA domains of KPC2 are indispensable for its function.