TOK-1, a novel p21Cip1-binding protein that cooperatively enhances p21-dependent inhibitory activity toward CDK2 kinase
TOK-1, a novel p21Cip1-binding protein that cooperatively enhances p21-dependent inhibitory activity toward CDK2 kinase
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DOI：
10.1074/jbc.m003031200
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发表时间：
2000-10-06
影响因子：
4.8
通讯作者：
Ariga, H
中科院分区：
文献类型：
--
作者：
Ono, T;Kitaura, H;Ariga, H
已知p21（Cip 1/Waf 1/Sdi 1）通过抑制多种细胞周期蛋白依赖性激酶的激酶活性而作为负性细胞周期调节剂。除了细胞周期蛋白依赖性激酶与p21的N-末端区域的结合之外，p21还与增殖细胞核抗原（PCNA）、SET/TAF 1和钙调蛋白在其C-末端区域结合，表明p21的多功能。在本研究中，我们通过双杂交系统克隆了一个新的蛋白质编码TOK-1作为p21的C-末端结合蛋白。TOK-1的两种剪接异构体，TOK-1 α和TOK-1 β，分别包含322和314个氨基酸，与p21共定位于细胞核中，并显示出与p21在人体组织中相似的表达谱。TOK-1 α，而不是TOK-1 β，直接结合到p21的C-末端近端区域，并且两者都在细胞周期的G（1）/S边界表达。TOK-1 α还通过p21优先结合到细胞周期蛋白依赖性激酶2（CDK 2）的活性形式，这些在人类细胞中形成三元复合物。此外，三种不同类型的实验的结果表明，TOK-1 α增强了pal对CDK 2的组蛋白III激酶活性的抑制活性。因此，TOK-1 α被认为是一种新型的CDK 2调节剂。
A p21(Cip1/Waf1/Sdi1) is known to act as a negative cell-cycle regulator by inhibiting kinase activity of a variety of cyclin-dependent kinases. In addition to binding of the cyclin-dependent kinase to the N-terminal region of p21, p21 is also bound at its C-terminal region by proliferating cell nuclear antigen (PCNA), SET/TAF1, and calmodulin, indicating the versatile function of p21. In this study, we cloned cDNA encoding a novel protein named TOK-1 as a p21 C-terminal-binding protein by a two-hybrid system. Two splicing isoforms of TOK-1, TOK-1 alpha and TOK-1 beta, comprising 322 and 314 amino acids, respectively, were co-localized with p21 in nuclei and showed a similar expression profile to that of p21 in human tissues. TOK-1 alpha, but not TOK-1 beta, directly bound to the C-terminal proximal region of p21, and both were expressed at the G(1)/S boundary of the cell cycle. TOK-1 alpha also preferentially bound to an active form of cyclin-dependent kinase 2 (CDK2) via p21, and these made a ternary complex in human cells. Furthermore, the results of three different types of experiments showed that TOK-1 alpha enhanced the inhibitory activity of pal toward histone Ill kinase activity of CDK2. TOK-1 alpha is thus thought to be a new type of CDK2 modulator.