Bosc D G, Lüscher B, Litchfield D W
Department of Biochemistry and Molecular Biology, University of Manitoba, Winnipeg, Canada.
Mol Cell Biochem. 1999 Jan;191(1-2):213-22.
There are indications from genetic, biochemical and cell biological studies that protein kinase CK2 (formerly casein kinase II) has a variety of functions at different stages in the cell cycle. To further characterize CK2 and its potential roles during cell cycle progression, one of the objectives of this study was to systematically examine the expression of all three subunits of CK2 at different stages in the cell cycle. To achieve this objective, we examined levels of CK2alpha, CK2alpha' and CK2beta on immunoblots as well as CK2 activity in samples prepared from: (i) elutriated populations of MANCA (Burkitt lymphoma) cells, (ii) serum-stimulated GL30-92/R (primary human fibroblasts) cells and (iii) drug-arrested chicken bursal lymphoma BK3A cells. On immunoblots, we observed a significant and co-ordinate increase in the expression of CK2alpha and CK2alpha' following serum stimulation of quiescent human fibroblasts. By comparison, no major fluctuations in CK2 activity were detected during any other stages during the cell cycle. Furthermore, we did not observe any dramatic differences between the relative levels of CK2alpha to CK2alpha' during different stages in the cell cycle. However, we observed a significant increase in the amount of CK2beta relative to CK2alpha in cells arrested with nocodazole. We also examined the activity of CK2 in extracts or in immunoprecipitates prepared from drug-arrested cells. Of particular interest is the observation that the activity of CK2 is not changed in nocodazole-arrested cells. Since CK2 is maximally phosphorylated in these cells, this result suggests that the phosphorylation of CK2 by p34cdc2 does not affect the catalytic activity of CK2. However, the activity of CK2 was increased by incubation with p34cdc2 in vitro. Since this activation was independent of ATP we speculate that p34cdc2 may have an associated factor that stimulates CK2 activity. Collectively, the observations that relative levels of CK2beta increase in mitotic cells, that CK2alpha and CK2beta are phosphorylated in mitotic cells and that p34cdc2 affects CK2 activity in vitro suggest that CK2 does have regulatory functions associated with cell division.
遗传学、生物化学和细胞生物学研究表明，蛋白激酶CK2（以前称为酪蛋白激酶II）在细胞周期的不同阶段具有多种功能。为了进一步阐明CK2的特性及其在细胞周期进程中的潜在作用，本研究的目标之一是系统地检测CK2的三个亚基在细胞周期不同阶段的表达情况。为实现这一目标，我们通过免疫印迹法检测了CK2α、CK2α'和CK2β的水平，并检测了从以下样本中制备的样品中的CK2活性：（i）淘洗后的MANCA（伯基特淋巴瘤）细胞群体，（ii）血清刺激后的GL30-92/R（原代人成纤维细胞）细胞，以及（iii）药物阻滞的鸡法氏囊淋巴瘤BK3A细胞。在免疫印迹中，我们观察到静止的人成纤维细胞在血清刺激后，CK2α和CK2α'的表达显著且协同增加。相比之下，在细胞周期的任何其他阶段均未检测到CK2活性的主要波动。此外，我们未观察到细胞周期不同阶段CK2α与CK2α'的相对水平存在任何显著差异。然而，我们观察到用诺考达唑阻滞的细胞中，CK2β相对于CK2α的量显著增加。我们还检测了从药物阻滞细胞制备的提取物或免疫沉淀物中的CK2活性。特别值得关注的是，在诺考达唑阻滞的细胞中，CK2的活性未发生变化。由于CK2在这些细胞中被最大程度地磷酸化，这一结果表明p34cdc2对CK2的磷酸化不影响CK2的催化活性。然而，在体外与p34cdc2一起孵育可增加CK2的活性。由于这种激活不依赖于ATP，我们推测p34cdc2可能具有一种刺激CK2活性的相关因子。总体而言，有丝分裂细胞中CK2β的相对水平增加、有丝分裂细胞中CK2α和CK2β被磷酸化以及p34cdc2在体外影响CK2活性这些观察结果表明，CK2确实具有与细胞分裂相关的调节功能。
