Jackman Mark, Kubota Yumiko, den Elzen Nicole, Hagting Anja, Pines Jonathon
Wellcome/Cancer Research U.K. (London) Institute and Department of Zoology, University of Cambridge, Cambridge, United Kingdom CB2 1QR.
Mol Biol Cell. 2002 Mar;13(3):1030-45. doi: 10.1091/mbc.01-07-0361.
Cyclins A and E and their partner cyclin-dependent kinases (Cdks) are key regulators of DNA synthesis and of mitosis. Immunofluorescence studies have shown that both cyclins are nuclear and that a proportion of cyclin A is localized to sites of DNA replication. However, recently, both cyclin A and cyclin E have been implicated as regulators of centrosome replication, and it is unclear when and where these cyclin-Cdks can interact with cytoplasmic substrates. We have used live cell imaging to study the behavior of cyclin/Cdk complexes. We found that cyclin A and cyclin E are able to regulate both nuclear and cytoplasmic events because they both shuttle between the nucleus and the cytoplasm. However, we found that there are marked differences in their shuttling behavior, which raises the possibility that cyclin/Cdk function could be regulated at the level of nuclear import and export. In the course of these experiments, we have also found that, contrary to published results, mutations in the hydrophobic patch of cyclin A do affect Cdk binding and nuclear import. This has implications for the role of the hydrophobic patch as a substrate selection motif.
细胞周期蛋白A和E及其伴侣细胞周期蛋白依赖性激酶（Cdks）是DNA合成和有丝分裂的关键调节因子。免疫荧光研究表明，这两种细胞周期蛋白都存在于细胞核中，且一部分细胞周期蛋白A定位于DNA复制位点。然而，最近细胞周期蛋白A和细胞周期蛋白E都被认为是中心体复制的调节因子，目前尚不清楚这些细胞周期蛋白-Cdks何时以及在何处能够与细胞质底物相互作用。我们利用活细胞成像技术研究了细胞周期蛋白/Cdk复合物的行为。我们发现细胞周期蛋白A和细胞周期蛋白E能够调节细胞核和细胞质中的事件，因为它们都能在细胞核和细胞质之间穿梭。然而，我们发现它们的穿梭行为存在显著差异，这增加了细胞周期蛋白/Cdk功能可能在核输入和输出水平受到调节的可能性。在这些实验过程中，我们还发现，与已发表的结果相反，细胞周期蛋白A疏水结构域的突变确实会影响Cdk结合和核输入。这对疏水结构域作为底物选择基序的作用具有重要意义。
