p27Kip1 Inhibits Cyclin D-Cyclin-Dependent Kinase 4 by Two Independent Modes (Publication with Expression of Concern. See vol. 42, 2022)
p27Kip1 Inhibits Cyclin D-Cyclin-Dependent Kinase 4 by Two Independent Modes (Publication with Expression of Concern. See vol. 42, 2022)
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DOI：
10.1128/mcb.00898-08
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发表时间：
2009-02-15
影响因子：
5.3
通讯作者：
Blain, Stacy W.
中科院分区：
文献类型：
--
作者：
Ray, Arpita;James, Melissa K.;Blain, Stacy W.
细胞周期进程受细胞周期蛋白依赖性激酶（cdk）调节，而cdk又受其与化学计量抑制剂（如p27（Kip 1））的相互作用调节。虽然p27与细胞周期蛋白D-依赖性激酶4（cdk 4）组成性相关，但它是否抑制该复合物取决于在不同生长条件下是否存在将p27从结合抑制剂转化为结合非抑制剂的特定酪氨酸磷酸化。这种磷酸化发生在p27的3-10螺旋内，并且可以将螺旋从cdk 4的活性位点移除以允许ATP结合。在这里，我们表明，非磷酸化的p27与cdk 4的相互作用也阻止了T环的细胞周期蛋白H-cdk 7，cdk激活激酶（CAK）的激活磷酸化。尽管细胞周期蛋白H-cdk 7复合物存在于接触停滞细胞中并具有活性，但p27与细胞周期蛋白D-cdk 4的结合阻止了T环磷酸化。当p27在增殖细胞中或在体外用酪氨酸Y激酶Abl酪氨酸磷酸化时，允许cdk 4被细胞周期蛋白H-cdk 7磷酸化，甚至没有p27的解离。这表明，从接触停滞状态释放后，失活的p27-细胞周期蛋白D-cdk 4复合物的重新激活的时间顺序必须存在：p27必须首先被Y磷酸化，直接允许细胞周期蛋白H-cdk 7残基T172磷酸化，随后恢复激酶活性。非Y-磷酸化的p27-cyclin D-cdk 4复合物可以被纯化的Csk 1磷酸化，Csk 1是一种来自裂殖酵母的单亚基CAK，但由于p27的活性位点的封闭而仍然是无活性的。因此，p27抑制细胞周期蛋白D-cdk 4的两种模式是独立的，并且可以相互加强以抑制接触停滞细胞中的激酶活性，同时保持可在细胞周期重新进入时快速激活的预形成复合物的储库。
Cell cycle progression is regulated by cyclin-dependent kinases (cdk's), which in turn are regulated by their interactions with stoichiometric inhibitors, such as p27(Kip1). Although p27 associates with cyclin D-cyclin-dependent kinase 4 (cdk4) constitutively, whether or not it inhibits this complex is dependent on the absence or presence of a specific tyrosine phosphorylation that converts p27 from a bound inhibitor to a bound noninhibitor under different growth conditions. This phosphorylation occurs within the 3-10 helix of p27 and may dislodge the helix from cdk4's active site to allow ATP binding. Here we show that the interaction of nonphosphorylated p27 with cdk4 also prevents the activating phosphorylation of the T-loop by cyclin H-cdk7, the cdk-activating kinase (CAK). Even though the cyclin H-cdk7 complex is present and active in contact-arrested cells, p27's association with cyclin D-cdk4 prevents T-loop phosphorylation. When p27 is tyrosine phosphorylated in proliferating cells or in vitro with the tyrosine Y kinase Abl, phosphorylation of cdk4 by cyclin H-cdk7 is permitted, even without dissociation of p27. This suggests that upon release from the contact-arrested state, a temporal order for the reactivation of inactive p27-cyclin D-cdk4 complexes must exist: p27 must be Y phosphorylated first, directly permitting cyclin H-cdk7 phosphorylation of residue T172 and the consequent restoration of kinase activity. The non-Y-phosphorylated p27-cyclin D-cdk4 complex could be phosphorylated by purified Csk1, a single-subunit CAK from fission yeast, but was still inactive due to p27's occlusion of the active site. Thus, the two modes by which p27 inhibits cyclin D-cdk4 are independent and may reinforce one another to inhibit kinase activity in contact-arrested cells, while maintaining a reservoir of preformed complex that can be activated rapidly upon cell cycle reentry.