TUMOR SUPPRESSOR GENE AND CHEMICAL CARCINOGENESIS

描述：WT1(Wilms Tumor 1)，一种含锌指的肿瘤抑制因子 蛋白质在发育中的泌尿生殖系统和行为中起着至关重要的作用 作为生长相关基因的转录抑制因子。而当 大鼠恶性S肿瘤模型的特征--亚硝基甲基脲 (NMU)诱导的胚胎肾瘤，我们发现大鼠WT1转录本 进行RNA编辑。RNA编辑是一种新颖的RNA修饰形式， 以共转录或转录后方式发生。WT1基因组序列含有CTC (Leu)在第280位密码子，而在cDNA第2 0位同时显示CTC(Leu)和CCC(Pro 这个密码子。在同一核苷酸(T到C)处的RNA编辑也发生在 人类WT1。WT1信使核糖核酸编辑被预测具有生物学意义， 与WT1-LEU蛋白不同，编辑后的WT1-Pro具有较低的抑制能力 与生长相关基因启动子相关的基因的转录 作为EGR-1和IGF2。另一方面，编辑后的WT1-PRO蛋白抑制 分化特异性MK(中期因子)相关基因的转录 基因启动子比未经编辑的WT1-LEU更有效。 我们观察到，当胚胎和新生大鼠的肾脏含有 未检测到编辑水平的WT1 mRNA，大部分为NMU诱导的肾脏 肿瘤(13/18)和人类肾母细胞瘤(7/15)包含编辑的WT1 MRNA.我们推测，RNA编辑的失调和不合时宜 表达编辑的蛋白质会导致生长的持续表达 因子和分化因子的抑制，两者都是 在这个系统中助长了恶变。为了测试这一概念，我们将 确定WT1的编辑形式在啮齿动物中是否过度表达 人类细胞在体外会导致细胞周期停滞和/或细胞凋亡。 最后，我们想要描述序列的上下文和酶 调节WT1 mRNA中的RNA编辑的活动，未来的目标是 克隆编码这一活动的基因。

DESCRIPTION: WT1 (Wilms tumor 1), a zinc finger-containing tumor suppressor protein plays a crucial role in the developing urogenital system and behaves as a transcriptional repressor of genes involved in growth. While characterizing the rat model for Wilm s tumors- the nitrosomethylurea (NMU)-induced embryonal nephromas, we discovered that the rat WT1 transcript undergoes RNA editing. RNA editing is a novel form of RNA modification that occurs co- or post-transcriptionally. The WT1 genomic sequence contains CTC (LEU) at codon 280 while the cDNA displays both CTC (LEU) and CCC (PRO) at this codon. RNA editing at the same nucleotide (T to C) also occurs in human WT1. WT1 mRNA editing is predicted to have biological significance, unlike the WT1-LEU protein, edited WT1-PRO has a lower capacity to repress the transcription of genes linked to the growth-related gene promoters such as EGR-1, and IGF2. On the other hand, the edited WT1-PRO protein represses transcription of genes linked to the differentiation-specific MK (midkine) gene promoter much more efficiently than unedited WT1-LEU. We have observed that while embryonal and newborn rat kidney contain undetectable levels of edited WT1 mRNA, the majority of NMU-induced kidney tumors (13/18), as well as human Wilms tumors (7/15) contain edited WT1 mRNA. We postulate that dysregulation of RNA editing and untimely expression of edited protein result in continued expression of growth factors and a suppression of differentiation factors, both of which contribute to malignancy in this system. To test this concept, we will determine whether over expression of the edited form of WT1 in rodent and human cells in vitro results in cell cycle arrest and/or apoptosis. Finally, we would like to characterize the sequence context and enzymatic activity that mediates RNA editing in the WT1 mRNA, with a future goal of cloning the gene encoding this activity.