Differential Phosphorylation of Plant Translation Initiation Factors by Arabidopsis thaliana CK2 Holoenzymes
Differential Phosphorylation of Plant Translation Initiation Factors by Arabidopsis thaliana CK2 Holoenzymes
复制标题
DOI：
10.1074/jbc.m109.006692
复制
发表时间：
2009-07-31
影响因子：
4.8
通讯作者：
Browning, Karen S.
中科院分区：
文献类型：
--
作者：
Dennis, Michael D.;Browning, Karen S.
先前描述的麦胚蛋白激酶（Yan，T. F.、和Tao，M.（1982）J.Biol.Chem.257，7037-7043）使用质谱法明确地鉴定为CK 2。CK 2是一种普遍存在的真核蛋白激酶，可磷酸化多种底物。在以前的研究中，这种麦胚激酶被证明磷酸化eIF 2 α、eIF 3 c和三种大亚基（60 S）核糖体蛋白（布朗宁，K.美国，Yan，T. F.、劳尔，S. J.，阿基诺湖一、Tao，M.，和Ravel，J. M.（1985）Plant Physiol.77，370-373）。为了进一步表征CK 2在翻译起始调节中的作用，克隆了拟南芥CK 2的催化亚基（α 1和α 2）和调节亚基（β 1，β 2，β 3和β 4），并在大肠杆菌中表达。重组A.在CK 2 α 1或CK 2 α 2存在下，拟南芥CK 2 β亚基自发地二聚化并组装成全酶，并表现出自磷酸化。纯化的CK 2亚基用于表征单个亚基的性质及其磷酸化各种植物蛋白底物的能力。CK 2可磷酸化eIF 2 α、eIF 2 β、eIF 3c、eIF 4 B、eIF 5和组蛋白脱乙酰酶2B，但不磷酸化eIF 1、eIF 1A、eIF 4A、eIF 4 E、eIF 4G、eIFiso 4 E或eIFiso 4G。CK 2在存在各种调节β亚基的情况下表现出差异磷酸化。分析A.缺乏或过表达CK 2亚基的拟南芥突变体显示，提取物中存在的eIF 2 β蛋白的量受到影响，这表明CK 2磷酸化可能在eIF 2 β稳定性中起作用。这些结果为CK 2 β亚基的表达和/或亚细胞分布参与植物翻译起始和其他生理过程的调节提供了潜在机制的证据。
A previously described wheat germ protein kinase (Yan, T. F., and Tao, M. (1982) J. Biol. Chem. 257, 7037-7043) was identified unambiguously as CK2 using mass spectrometry. CK2 is a ubiquitous eukaryotic protein kinase that phosphorylates a wide range of substrates. In previous studies, this wheat germ kinase was shown to phosphorylate eIF2 alpha, eIF3c, and three large subunit (60 S) ribosomal proteins (Browning, K. S., Yan, T. F., Lauer, S. J., Aquino, L. A., Tao, M., and Ravel, J. M. (1985) Plant Physiol. 77, 370-373). To further characterize the role of CK2 in the regulation of translation initiation, Arabidopsis thaliana catalytic (alpha 1 and alpha 2) and regulatory (beta 1, beta 2, beta 3, and beta 4) subunits of CK2 were cloned and expressed in Escherichia coli. Recombinant A. thaliana CK2 beta subunits spontaneously dimerize and assemble into holoenzymes in the presence of either CK2 alpha 1 or CK2 alpha 2 and exhibit autophosphorylation. The purified CK2 subunits were used to characterize the properties of the individual subunits and their ability to phosphorylate various plant protein substrates. CK2 was shown to phosphorylate eIF2 alpha, eIF2 beta, eIF3c, eIF4B, eIF5, and histone deacetylase 2B but did not phosphorylate eIF1, eIF1A, eIF4A, eIF4E, eIF4G, eIFiso4E, or eIFiso4G. Differential phosphorylation was exhibited by CK2 in the presence of various regulatory beta-subunits. Analysis of A. thaliana mutants either lacking or overexpressing CK2 subunits showed that the amount of eIF2 beta protein present in extracts was affected, which suggests that CK2 phosphorylation may play a role in eIF2 beta stability. These results provide evidence for a potential mechanism through which the expression and/or subcellular distribution of CK2 beta-subunits could participate in the regulation of the initiation of translation and other physiological processes in plants.