Yu Z K, Gervais J L, Zhang H
Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Proc Natl Acad Sci U S A. 1998 Sep 15;95(19):11324-9. doi: 10.1073/pnas.95.19.11324.
Deregulation of cell proliferation is a hallmark of cancer. In many transformed cells, the cyclin A/CDK2 complex that contains S-phase kinase associated proteins 1 and 2 (SKP1 and SKP2) is highly induced. To determine the roles of this complex in the cell cycle regulation and transformation, we have examined the composition of this complex. We report here that this complex contained an additional protein, human CUL-1, a member of the cullin/CDC53 family. The identification of CUL-1 as a member of the complex raises the possibility that the p19(SKP1)/p45(SKP2)/CUL-1 complex may function as the yeast SKP1-CDC53-F-box (SCF) protein complex that acts as a ubiquitin E3 ligase to regulate the G1/S transition. In mammalian cells, cyclin D, p21(CIP1/WAF1), and p27(KIP1) are short-lived proteins that are controlled by ubiquitin-dependent proteolysis. To determine the potential in vivo targets of the p19(SKP1)/p45(SKP2)/CUL-1 complex, we have used the specific antisense oligodeoxynucleotides against either SKP1, SKP2, or CUL-1 RNA to inhibit their expression. Treatment of cells with these oligonucleotides caused the selective accumulation of p21 and cyclin D proteins. The protein level of p27 was not affected. These data suggest that the human p19(SKP1)/p45(SKP2)/CUL-1 complex is likely to function as an E3 ligase to selectively target cyclin D and p21 for the ubiquitin-dependent protein degradation. Aberrant expression of human p19(SKP1)/p45(SKP2)/CUL-1 complex thus may contribute to tumorigenesis by regulating the protein levels of G1 cell cycle regulators.
细胞增殖失调是癌症的一个标志。在许多转化细胞中，含有S期激酶相关蛋白1和2（SKP1和SKP2）的细胞周期蛋白A/细胞周期蛋白依赖性激酶2（CDK2）复合物被高度诱导。为了确定该复合物在细胞周期调控和转化中的作用，我们研究了该复合物的组成。我们在此报告，该复合物包含一种额外的蛋白质，即人CUL-1，它是cullin/CDC53家族的成员。CUL-1作为复合物成员的鉴定增加了p19(SKP1)/p45(SKP2)/CUL-1复合物可能作为酵母SKP1-CDC53-F-box（SCF）蛋白复合物发挥作用的可能性，该复合物作为泛素E3连接酶来调节G1/S期转换。在哺乳动物细胞中，细胞周期蛋白D、p21(CIP1/WAF1)和p27(KIP1)是通过泛素依赖性蛋白水解来控制的短寿命蛋白。为了确定p19(SKP1)/p45(SKP2)/CUL-1复合物在体内的潜在靶点，我们使用了针对SKP1、SKP2或CUL-1 RNA的特异性反义寡脱氧核苷酸来抑制它们的表达。用这些寡核苷酸处理细胞导致p21和细胞周期蛋白D蛋白的选择性积累。p27的蛋白水平未受影响。这些数据表明，人p19(SKP1)/p45(SKP2)/CUL-1复合物可能作为一种E3连接酶，选择性地将细胞周期蛋白D和p21作为泛素依赖性蛋白降解的靶点。因此，人p19(SKP1)/p45(SKP2)/CUL-1复合物的异常表达可能通过调节G1期细胞周期调节因子的蛋白水平而导致肿瘤发生。
