Deng Min, Li Fahui, Ballif Bryan A, Li Shan, Chen Xi, Guo Lin, Ye Xin
Department of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
J Biol Chem. 2009 Mar 20;284(12):7875-88. doi: 10.1074/jbc.M807827200. Epub 2009 Jan 16.
Cyclin E/Cdk2 is a key regulator in G(1)-S transition. We have identified a novel cyclin E/Cdk2 substrate called Ankrd17 (ankyrin repeat protein 17) using the TAP tag purification technique. Ankrd17 protein contains two clusters of a total 25 ankyrin repeats at its N terminus, one NES (nuclear exporting signal) and one NLS (nuclear localization signal) in the middle, and one RXL motif at its C terminus. Ankrd17 is expressed in various tissues and associates with cyclin E/Cdk2 in an RXL-dependent manner. It can be phosphorylated by cyclin E/Cdk2 at 3 phosphorylation sites (Ser(1791), Ser(1794), and Ser(2150)). Overexpression of Ankrd17 promotes S phase entry, whereas depletion of Ankrd17 expression by small interfering RNA inhibits DNA replication and blocks cell cycle progression as well as up-regulates the expression of p53 and p21. Ankrd17 is localized to the nucleus and interacts with DNA replication factors including MCM family members, Cdc6 and PCNA. Depletion of Ankrd17 results in decreased loading of Cdc6 and PCNA onto DNA suggesting that Ankrd17 may be directly involved in the DNA replication process. Taken together, these data indicate that Ankrd17 is an important downstream effector of cyclin E/Cdk2 and positively regulates G(1)/S transition.
细胞周期蛋白E/细胞周期蛋白依赖性激酶2（Cyclin E/Cdk2）是G1期向S期转换的关键调节因子。我们利用串联亲和纯化技术鉴定出一种名为Ankrd17（锚蛋白重复序列蛋白17）的新型细胞周期蛋白E/Cdk2底物。Ankrd17蛋白在其N端含有总共25个锚蛋白重复序列的两个簇，中间有一个核输出信号（NES）和一个核定位信号（NLS），C端有一个RXL基序。Ankrd17在多种组织中表达，并以RXL依赖的方式与细胞周期蛋白E/Cdk2结合。它可在3个磷酸化位点（Ser(1791)、Ser(1794)和Ser(2150)）被细胞周期蛋白E/Cdk2磷酸化。Ankrd17的过表达促进S期进入，而通过小干扰RNA耗尽Ankrd17的表达则抑制DNA复制、阻断细胞周期进程，并上调p53和p21的表达。Ankrd17定位于细胞核，并与包括MCM家族成员、Cdc6和增殖细胞核抗原（PCNA）在内的DNA复制因子相互作用。Ankrd17的缺失导致Cdc6和PCNA在DNA上的装载减少，这表明Ankrd17可能直接参与DNA复制过程。综上所述，这些数据表明Ankrd17是细胞周期蛋白E/Cdk2的重要下游效应物，并正向调节G1/S转换。
