Characterization of the Wilms tumor gene product WT1

我们检测了WT1在细胞增殖和分化中的作用，得到了以下结果：在NIH3T3细胞中微量注射WT1 cDNA可阻断血清诱导的细胞周期进入S期。cyclin E/CDK2和cyclin D1/CDK4的过表达使WT1的抑制活性消失。此外，在过表达WT1的细胞中，CDK4-和CDK2相关激酶活性均下调，而CDK4、CDK2和cyclin D1的表达水平不变。这些发现表明，细胞周期蛋白/CDK复合物活性的抑制可能参与介导wt1诱导的细胞周期阻滞2。在维甲酸诱导的胚胎癌F9细胞分化过程中，WT1的表达降低。组成表达外源WT1的细胞系无法分化为原始内胚层细胞并发生凋亡死亡，提示WT1表达下调是F9细胞正常分化为顶壁内胚层细胞所必需的。我们还发现WT1是一种新的预后因子和检测急性白血病微小残留病的新标志物。利用酵母双杂交系统，我们获得了一个新的cDNA克隆，该克隆编码一个假定的wt1相关蛋白。我们的实验室正在对这种蛋白质进行详细的表征。

We examined the function of WT1 in cellular proliferation and differentiation, and obtained the following results.1. Microinjection of the WT1 cDNA in NIH3T3 cells blocked serum-induced cell cycle progression into S phase. The inhibitory activity of WT1 was abrogated by the overexpression of cyclin E/CDK2 as well as cyclin D1/CDK4. Furthermore, both CDK4- and CDK2-associated kinase activities were downregulated in cells overexpressing WT1, whereas the levels of CDK4, CDK2 and cyclin D1 expression were unchanged. These findings suggest that inhibition of the activity of cyclin/CDK complexes may be involved in mediating the WT1-induced cell cycle block.2. The expression of WT1 decreased during retinoic acid-induced differentiation of embryonal carcinoma F9 cells. Cell lines constitutively expressing the exogenous WT1 failed to differentiate into primitive endoderm cells and underwent apoptotic death, suggesting that downregulation of WT1 expression is necessary for normal differentiation of F9 cells into parietal endoderm cells. We also found that WT1 is a new prognostic factor and a new marker for the detection of minimal residual disease in acute leukeia.3. Using a yeast two-hybrid system, we obtained a novel cDNA clone which encodes a putative WT1-associated protein. Detailed characterization of this protein is underway in our laboratory.