细胞质泛素连接酶KPC在G1期调节p27（Kip1）的蛋白水解。

Cytoplasmic ubiquitin ligase KPC regulates proteolysis of p27(Kip1) at G1 phase.

作者信息

Kamura Takumi, Hara Taichi, Matsumoto Masaki, Ishida Noriko, Okumura Fumihiko, Hatakeyama Shigetsugu, Yoshida Minoru, Nakayama Keiko, Nakayama Keiichi I

机构信息

Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan.

出版信息

Nat Cell Biol. 2004 Dec;6(12):1229-35. doi: 10.1038/ncb1194. Epub 2004 Nov 7.

DOI:10.1038/ncb1194

PMID:15531880

Abstract

The cyclin-dependent kinase inhibitor p27(Kip1) is degraded at the G0-G1 transition of the cell cycle by the ubiquitin-proteasome pathway. Although the nuclear ubiquitin ligase (E3) SCF(Skp2) is implicated in p27(Kip1) degradation, proteolysis of p27(Kip1) at the G0-G1 transition proceeds normally in Skp2(-/-) cells. Moreover, p27(Kip1) is exported from the nucleus to the cytoplasm at G0-G1 (refs 9-11). These data suggest the existence of a Skp2-independent pathway for the degradation of p27(Kip1) at G1 phase. We now describe a previously unidentified E3 complex: KPC (Kip1 ubiquitination-promoting complex), consisting of KPC1 and KPC2. KPC1 contains a RING-finger domain, and KPC2 contains a ubiquitin-like domain and two ubiquitin-associated domains. KPC interacts with and ubiquitinates p27(Kip1) and is localized to the cytoplasm. Overexpression of KPC promoted the degradation of p27(Kip1), whereas a dominant-negative mutant of KPC1 delayed p27(Kip1) degradation. The nuclear export of p27(Kip1) by CRM1 seems to be necessary for KPC-mediated proteolysis. Depletion of KPC1 by RNA interference also inhibited p27(Kip1) degradation. KPC thus probably controls degradation of p27(Kip1) in G1 phase after export of the latter from the nucleus.

摘要

细胞周期蛋白依赖性激酶抑制剂p27（Kip1）在细胞周期的G0-G1转换阶段通过泛素-蛋白酶体途径被降解。尽管核泛素连接酶（E3）SCF（Skp2）与p27（Kip1）的降解有关，但p27（Kip1）在G0-G1转换阶段的蛋白水解在Skp2基因敲除（Skp2(-/-)）细胞中仍正常进行。此外，p27（Kip1）在G0-G1期从细胞核输出到细胞质（参考文献9-11）。这些数据表明存在一条在G1期独立于Skp2的p27（Kip1）降解途径。我们现在描述一种先前未被鉴定的E3复合物：KPC（Kip1泛素化促进复合物），它由KPC1和KPC2组成。KPC1含有一个环指结构域，KPC2含有一个泛素样结构域和两个泛素相关结构域。KPC与p27（Kip1）相互作用并使其泛素化，且定位于细胞质。KPC的过表达促进了p27（Kip1）的降解，而KPC1的显性负性突变体则延迟了p27（Kip1）的降解。CRM1介导的p27（Kip1）从细胞核输出似乎是KPC介导的蛋白水解所必需的。通过RNA干扰使KPC1缺失也抑制了p27（Kip1）的降解。因此，KPC可能在p27（Kip1）从细胞核输出后控制其在G1期的降解。