Fbx7 functions in the SCF complex regulating Cdk1-cyclin B-phosphorylated hepatoma up-regulated protein (HURP) proteolysis by a proline-rich region
Fbx7 functions in the SCF complex regulating Cdk1-cyclin B-phosphorylated hepatoma up-regulated protein (HURP) proteolysis by a proline-rich region
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DOI：
10.1074/jbc.m404950200
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发表时间：
2004-07-30
影响因子：
4.8
通讯作者：
Huang, CYF
中科院分区：
文献类型：
--
作者：
Hsu, JM;Lee, YCG;Huang, CYF
F-box蛋白是SCF泛素-连接酶复合物的组成部分，被认为是SCF介导的蛋白质水解中底物识别和募集的关键。迄今为止，已被鉴定为在SCF复合物中起作用的F-box蛋白大多具有底物结合基序，例如在其C末端的WD重复序列或富含亮氨酸的重复序列。然而，许多F-box蛋白缺乏可识别的底物结合模块，它们是否可以在SCF复合物中发挥作用仍不清楚。我们在这里表明，Fbx 7，没有WD重复序列和富含亮氨酸的重复序列的F-box蛋白，是必需的蛋白酶体介导的蛋白水解的肝癌上调蛋白（HURP）。小干扰RNA对Fbx 7的消耗导致HURP泛素化的抑制和HURP丰度的积累。在SCFFbx 7复合物中，Fbx 7以Cdk 1-细胞周期蛋白B-磷酸化依赖的方式通过其C-末端富含脯氨酸的区域募集HURP。HURP上的多个Cdk 1-细胞周期蛋白B磷酸化位点或Fbx 7的富含脯氨酸的区域的突变消除了Fbx 7和HURP之间的关联。因此，Fbx 7是SCF复合物的功能性衔接子，其富含脯氨酸的区域作为底物结合模块。除了Fbx 7，数据库分析揭示了两个推定的哺乳动物富含脯氨酸的区域含有F盒蛋白，KIAA 1783和RIKEN cDNA 2410015 K21。总之，这些发现进一步阐明了SCF复合物的不同底物识别能力。
F-box proteins, components of SCF ubiquitin-ligase complexes, are believed to be responsible for substrate recognition and recruitment in SCF-mediated proteolysis. F-box proteins that have been identified to function in the SCF complexes to date mostly have substrate-binding motifs, such as WD repeats or leucine-rich repeats in their C termini. However, many F-box proteins lack recognizable substrate-binding modules; whether they can function in the SCF complexes remains unclear. We show here that Fbx7, an F-box protein without WD repeats and leucine-rich repeats, is required for the proteasome-mediated proteolysis of the hepatoma upregulated protein (HURP). Depletion of Fbx7 by small interfering RNA leads to depression of HURP ubiquitination and accumulation of HURP abundance. In the SCFFbx7 complex, Fbx7 recruits HURP through its C-terminal proline-rich region in a Cdk1-cyclin B-phosphorylation dependent manner. Mutation of the multiple Cdk1-cyclin B phosphorylation sites on HURP or the proline-rich region of Fbx7 abolishes the association between Fbx7 and HURP. Thus, Fbx7 is a functional adaptor of the SCF complex with a proline-rich region as the substrate-binding module. In addition to Fbx7, data base analyses reveal two putative mammalian proline-rich region-containing F-box proteins, KIAA1783 and RIKEN cDNA 2410015K21. Taken together, these findings further expound the diverse substrate-recognition abilities of the SCF complexes.