Assembly of cyclin D-dependent kinase and titration of p27Kip1 regulated by mitogen-activated protein kinase kinase (MEK1)
Assembly of cyclin D-dependent kinase and titration of p27Kip1 regulated by mitogen-activated protein kinase kinase (MEK1)
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DOI：
10.1073/pnas.95.3.1091
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发表时间：
1998-02-03
影响因子：
11.1
通讯作者：
Roussel, MF
中科院分区：
文献类型：
--
作者：
Cheng, MG;Sexl, V;Roussel, MF
在NIH 3 T3成纤维细胞中，在锌诱导型启动子的控制下合成了一种组成型活性形式的丝裂原活化蛋白激酶（MEK 1）。锌处理血清饥饿的细胞激活细胞外信号调节蛋白激酶（ERK）和诱导细胞周期蛋白D1的表达。新合成的细胞周期蛋白D1与细胞周期蛋白依赖性激酶4（cyclin dependent kinase-4，CDK 4）组装形成全酶复合物，该复合物不能有效地磷酸化视网膜母细胞瘤蛋白，MEK 1/ERK通路的激活并不引发CDK抑制剂激酶抑制蛋白1的降解（p27（Kip 1））也不导致细胞周期蛋白E-和A-依赖性CDK 2的活化，并且这样的细胞不进入细胞分裂周期的DNA合成（S）期。与此相反，锌诱导活性MEK 1细胞也异位过表达细胞周期蛋白D1和CDK 4亚基产生的细胞周期蛋白D依赖性视网膜母细胞瘤蛋白激酶活性水平接近那些在血清刺激的细胞。在这种情况下，p27（Kip 1）被动员到含有细胞周期蛋白D1的复合物中，细胞周期蛋白E和A依赖性CDK 2复合物被激活;而血清饥饿的细胞进入S期。因此，尽管p27（Kip 1）的活性通常通过血清依赖性降解过程被取消，过表达的细胞周期蛋白D1-CDK复合物通过化学计量机制隔离p27（Kip 1）并降低有效抑制阈值，这些细胞的一部分完成S期并分裂，但它们不能持续增殖，表明其他血清应答因子最终成为细胞周期进展的速率限制。MEK/ERK通路不仅在转录水平上诱导细胞周期蛋白D1基因的表达，而且在转录后调节细胞周期蛋白D1与CDK 4的组装，从而帮助消除p27（Kip 1）介导的抑制。
A constitutively active form of mitogen-activated protein kinase kinase (MEK1) was synthesized under control of a zinc-inducible promoter in NIH 3T3 fibroblasts. Zinc treatment of serum-starved cells activated extracellular signal-regulated protein kinases (ERKs) and induced expression of cyclin D1. Newly synthesized cyclin D1 assembled with cyclin dependent kinase-4 (CDK4) to form holoenzyme complexes that phosphorylated the retinoblastoma protein inefficiently, Activation of the MEK1/ERK pathway neither triggered degradation of the CDK inhibitor kinase inhibitory protein-1 (p27(Kip1)) nor led to activation of cyclin E- and A-dependent CDK2, and such cells did not enter the DNA synthetic (S) phase of the cell division cycle. In contrast, zinc induction of active MEK1 in cells also engineered to ectopically overexpress cyclin D1 and CDK4 subunits generated levels of cyclin D-dependent retinoblastoma protein kinase activity approximating those achieved in cells stimulated by serum. In this setting, p27(Kip1) was mobilized into complexes containing cyclin D1; cyclin E-and A-dependent CDK2 complexes were activated; and serum-starved cells entered S phase, Thus, although the activity of p27(Kip1) normally is canceled through a serum-dependent degradative process, overexpressed cyclin D1-CDK complexes sequestered p27(Kip1) and reduced the effective inhibitory threshold through a stoichiometric mechanism, A fraction of these cells completed S phase and divided, but they were unable to continuously proliferate, indicating that other serum-responsive factors ultimately became rate limiting for cell cycle progression, Therefore, the MEK/ERK pathway not only acts transcriptionally to induce the cyclin D1 gene but functions posttranslationally to regulate cyclin D1 assembly with CDK4 and to thereby help cancel p27(Kip1)-mediated inhibition.