CK2 phosphorylation of eukaryotic translation initiation factor 5 potentiates cell cycle progression
CK2 phosphorylation of eukaryotic translation initiation factor 5 potentiates cell cycle progression
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DOI：
10.1073/pnas.0506791102
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发表时间：
2005-10-25
影响因子：
11.1
通讯作者：
Homma, Y
中科院分区：
文献类型：
--
作者：
Homma, MK;Wada, I;Homma, Y
酪蛋白激酶2（Casein kinase 2，CK 2）是一种普遍存在的真核生物丝氨酸/苏氨酸蛋白激酶，在细胞周期进程中起重要作用。虽然它在这一过程中的功能尚不清楚，但已知它是酵母G（1）和G（2）/M相变所必需的。在这里，我们发现，CK 2活性的变化显着在细胞周期的进展，并增加3小时内的血清刺激静止细胞。在其表现出高酶活性的时间段期间，CK 2与用于翻译起始的关键分子真核翻译起始因子（eIF）5缔合并磷酸化。使用MS，我们表明，Ser-389和-390 eIF 5的主要网站的磷酸化CK 2。使用缺乏CK 2位点的eIF 5突变体证实了这一点;在体外和体内，相对于WT eIF 5，突变体eIF 5蛋白的磷酸化水平显著降低。这些突变体的表达表明，它们对内源性eIF 5的磷酸化具有显性负效应，并且它们干扰细胞通过S期到M期的同步进展，导致生长速率显著降低。此外，在这些细胞中成熟eIF 5/eIF 2/eIF 3复合物的形成减少，并且事实上，如通过荧光相关光谱法所测量的，在缺乏CK 2磷酸化位点的GFP标记的eIF 5突变体中，WT eIF 5的受限扩散运动几乎被消除。这些结果表明，CK 2可能参与细胞周期进程的调节，通过关联和磷酸化的翻译起始的关键分子。
Casein kinase 2 (CK2) is a ubiquitous eukaryotic Ser/Thr protein kinase that plays an important role in cell cycle progression. Although its function in this process remains unclear, it is known to be required for the G(1) and G(2)/M phase transitions in yeast. Here, we show that CK2 activity changes notably during cell cycle progression and is increased within 3 h of serum stimulation of quiescent cells. During the time period in which it exhibits high enzymatic activity, CK2 associates with and phosphorylates a key molecule for translation initiation, eukaryotic translation initiation factor (eIF) 5. Using MS, we show that Ser-389 and -390 of eIF5 are major sites of phosphorylation by CK2. This is confirmed using eIF5 mutants that lack CK2 sites; the phosphorylation levels of mutant eIF5 proteins are significantly reduced, relative to WT eIF5, both in vitro and in vivo. Expression of these mutants reveals that they have a dominant-negative effect on phosphorylation of endogenous eIF5, and that they perturb synchronous progression of cells through S to M phase, resulting in a significant reduction in growth rate. Furthermore, the formation of mature eIF5/eIF2/eIF3 complex is reduced in these cells, and, in fact, restricted diffusional motion of WT eIF5 was almost abolished in a GFP-tagged eIF5 mutant lacking CK2 phosphorylation sites, as measured by fluorescence correlation spectroscopy. These results suggest that CK2 may be involved in the regulation of cell cycle progression by associating with and phosphorylating a key molecule for translation initiation.