CD28 costimulation mediates transcription of SKP2 and CKS1, the substrate recognition components of SCFSkp2 ubiquitin ligase that leads p27kip1 to degradation
CD28 costimulation mediates transcription of SKP2 and CKS1, the substrate recognition components of SCFSkp2 ubiquitin ligase that leads p27kip1 to degradation
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DOI：
10.4161/cc.5.18.3139
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发表时间：
2006-09-15
期刊：
影响因子：
4.3
通讯作者：
Boussiotis, Vassiliki A.
中科院分区：
文献类型：
--
作者：
Appleman, Leonard J.;Chernova, Irene;Boussiotis, Vassiliki A.
通过TCR/CD 3-plus-CD 28的活化诱导原代T淋巴细胞进入S期。细胞周期蛋白依赖性激酶抑制剂p27（kip 1）的下调在这一过程中是至关重要的，并介导的泛素靶向降解p27（kip 1）。p27（kip 1）的泛素化通过由核心组分Roc 1、Cul 1和Skp 1以及底物识别组分Skp 2和Cks 1组成的SCFskp 2泛素连接酶进行。在这里，我们表明，在原代人T淋巴细胞，SCF skp 2的核心组件Roc 1，Cul 1和Skp 1的组成型表达，其水平保持不变后，TCR/CD 3 + CD 28共刺激。相反，底物识别成分Skp 2和Cks 1在静息T细胞中几乎检测不到，并且在共刺激时被转录诱导。我们确定SKP 2启动子直接位于翻译起始位点的上游，并含有SP1，Elk-1和E2 F转录因子的结合位点。SP1和Elk-1位点的突变消除了TCR/CD 3-plus-CD 28-介导的SKP 2启动子驱动的报告活性，而E2 F位点的突变增强了报告活性，这表明SKP 2启动子可能作为有丝分裂和抗有丝分裂信号的整合节点。因此，在原代T淋巴细胞中，CD 28共刺激可以通过诱导靶向p27（kip 1）降解的SCFskp 2泛素连接酶的底物识别组分的转录来直接调节细胞周期进程。
Activation through TCR/CD3-plus-CD28 induces primary T lymphocytes to enter S phase. Downregulation of cyclin-dependent kinase inhibitor p27(kip1) is critical in this process and is mediated by ubiquitin-targeted degradation of p27(kip1). Ubiquitination of p27(kip1) is performed by the SCFskp2 ubiquitin ligase comprised of the core components Roc1, Cul1 and Skp1 and the substrate recognition components Skp2 and Cks1. Here we show that in primary human T lymphocytes, the SCFskp2 core components Roc1, Cul1 and Skp1 are constitutively expressed, and their levels remain unchanged upon TCR/CD3-plus-CD28 costimulation. In contrast, the substrate recognition components Skp2 and Cks1 are almost undetectable in resting T cells and are transcriptionally induced upon costimulation. We determined that the SKP2 promoter lies directly upstream of the translational start site and contains binding sites for SP1, Elk-1 and E2F transcription factors. Mutagenesis of SP1 and Elk-1 sites abrogated TCR/CD3-plus-CD28-mediated SKP2 promoter-driven reporter activity, whereas mutagenesis of an E2F site enhanced reporter activity, suggesting that SKP2 promoter may act as a node of integration for mitogenic and anti-mitogenic signals. Thus, in primary T lymphocytes CD28 costimulation can directly regulate cell cycle progression by inducing transcription of the substrate recognition components of SCFskp2 ubiquitin ligase that targets p27(kip1) for degradation.