Kitsios Georgios, Alexiou Konstantinos G, Bush Max, Shaw Peter, Doonan John H
John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.
Plant J. 2008 Apr;54(2):220-35. doi: 10.1111/j.1365-313X.2008.03414.x. Epub 2008 Jan 16.
Cyclin-dependent kinases (CDKs) play key regulatory roles in diverse cellular functions, including cell-cycle progression, transcription and translation. In plants, CDKs have been classified into several groups, named A through to G, but the functions of most are poorly characterized. CDKCs are known to phosphorylate the C-terminal domain (CTD) of RNA polymerase II (RNAP II), and therefore the CDKC-cyclinT (CycT) complex may have a role similar to the animal CDK9-CycT complex of the positive transcription elongation factor b (P-TEFb). However, we found that the predicted structure of the Arabidopsis CDKC2 protein is more similar to the mammalian cdc2-related kinase, CRK7, than to CDK9. CRK7 is proposed to link transcription with splicing, and CDKC2 contains all the structural features of CRK7 that make the latter distinct from CDK9. Consistent with this, we show that GFP-CDKC2 fusion proteins co-localize with spliceosomal components, that the expression of CDKC2 modifies the location of these components, and that co-localization was dependent on the transcriptional status of the cells and on CDKC2-kinase activity. We propose, therefore, that the Arabidopsis CDKC2 combines the functions of both CRK7 and CDK9, and could also couple splicing with transcription.
细胞周期蛋白依赖性激酶（CDK）在多种细胞功能中发挥关键调控作用，包括细胞周期进程、转录和翻译。在植物中，CDK已被分为几个组，命名为A至G，但大多数的功能仍不清楚。已知CDKC可磷酸化RNA聚合酶II（RNAP II）的C末端结构域（CTD），因此CDKC-细胞周期蛋白T（CycT）复合物可能具有与动物正转录延伸因子b（P-TEFb）的CDK9-CycT复合物类似的作用。然而，我们发现拟南芥CDKC2蛋白的预测结构与哺乳动物的细胞分裂周期蛋白2相关激酶CRK7更相似，而不是与CDK9相似。有人提出CRK7将转录与剪接联系起来，并且CDKC2包含CRK7的所有结构特征，这使得CRK7与CDK9不同。与此一致的是，我们表明GFP-CDKC2融合蛋白与剪接体成分共定位，CDKC2的表达改变了这些成分的位置，并且共定位取决于细胞的转录状态和CDKC2激酶活性。因此，我们提出拟南芥CDKC2兼具CRK7和CDK9的功能，并且还可能将剪接与转录联系起来。
