TUMOR SUPPRESSOR GENE AND CHEMICAL CARCINOGENESIS

描述：WT 1（Wilms tumor 1），一种含锌指的肿瘤抑制因子 蛋白质在泌尿生殖系统的发育中起着至关重要的作用， 作为参与生长的基因的转录抑制因子。 而 描述Wilm肿瘤的大鼠模型-亚硝基甲基脲 （NMU）诱导的胚胎性肾瘤，我们发现大鼠WT 1转录本 进行RNA编辑。 RNA编辑是一种新的RNA修饰形式， 在转录过程中或转录后发生。 WT 1基因组序列含有CTC (LEU)而cDNA在密码子280处显示CTC（LEU）和CCC（PRO）， 这个密码子 在相同的核苷酸（T到C）上的RNA编辑也发生在 人WT 1。 预测WT 1 mRNA编辑具有生物学意义， 与WT 1-LEU蛋白不同，编辑后的WT 1-PRO具有较低的抑制能力， 与生长相关基因启动子相连的基因的转录， EGR-1和IGF 2。 另一方面，经编辑的WT 1-PRO蛋白质抑制 与分化特异性MK（中期因子）相关的基因转录 基因启动子比未经编辑的WT 1-LEU更有效。 我们已经观察到，虽然胚胎和新生大鼠肾脏含有 不可检测水平的编辑WT 1 mRNA，大多数NMU诱导的肾脏 肿瘤（13/18）以及人Wilms肿瘤（7/15）含有编辑的WT 1 mRNA。 我们假设RNA编辑的失调和不合时宜的 编辑的蛋白质的表达导致生长的持续表达 因子和抑制分化因子，两者都 会导致这个系统的恶性肿瘤 为了验证这个概念，我们将 确定编辑形式的WT 1是否在啮齿动物中过表达， 体外人细胞导致细胞周期停滞和/或凋亡。 最后，我们想描述序列背景和酶促 在WT 1 mRNA中介导RNA编辑的活性，未来的目标是 克隆编码该活性的基因。

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.