MUTANT P53 GAIN OF FUNCTION IN TURMORIGENISIS

肿瘤的发生通常以多种基因改变为特征。 同时存在于显性癌基因和肿瘤抑制基因中。P53 抑癌基因是人类发现的最常见的突变基因 癌症。野生型p53抑癌基因产物被认为起作用 作为一种预防癌症的保护措施，而突变的p53功能作为一种 致癌基因并促进肿瘤的形成。突变型P53可能在脑内发挥作用 三种不同的致瘤机制：1)野生型缺失 肿瘤抑制功能；2)野生型P53蛋白失活 一种跨优势的消极态度；以及3)通过获得 促进细胞的致癌潜能。这样做的长期目标是 研究建议是为了加深我们对生物信息素功能的理解 突变型P53在促进恶性转化中的作用 目前对突变型P53基因表达的“功能增强”知之甚少 促进致瘤性。突变型P53的功能表型增益为 支持这一发现的是外源突变体P53在人卵巢癌中的表达 非致瘤且缺乏内源性P53蛋白的细胞株可以 将这些细胞转化为致瘤细胞系。此外，突变体 P53蛋白必须定位于核以增强致癌潜能 提示突变型p53可能作为一种调节因子发挥作用。 基因表达。与这一假设一致的是，突变的人类p53 等位基因与野生型P53蛋白不同，可以选择性地反式激活 人多药耐药启动子在瞬时基因检测中的应用 使用缺乏内源性P53蛋白的细胞。 为了增进我们对突变型P53功能增强的理解 表型，我们特别建议通过以下方式详细说明分子机制 突变型p53功能通过以下途径作为基因表达的反式激活因子 回答以下问题： 1)突变型p53反式转录需要mdr启动子的哪些DNA序列 激活？ 2)突变型p53反式激活内源性多药耐药基因是否稳定 转基因细胞？ 3)反式激活需要突变型P53的哪些结构域？ 4)p53相关蛋白mdm-2是否调节或调节突变型p53 激活功能？ 拟议的研究将有助于我们对如何 突变型p53可能与其他因子协同作用，如MDM-2， 以促进致瘤性。

Tumorigenesis is generally charactenzed by multiple genetic alterations occurring in both dominant oncogenes and tumor suppressor genes. The p53 tumor suppressor gene is the most commonly mutated gene detected in human cancer. The wild-type p53 tumor suppressor gene product is believed to act as a safeguard against cancer whereas, mutant p53 fiinctions as an oncogene and promotes tumorigenesis. Mutant p53 may function in tumorigenesis by three different mechanisms: 1) By a loss of wild-type tumor suppressor function; 2) Inactivation of the wild-type p53 protein in a trans-dominant negative manner; and 3) by a gain of fiinction that promotes the tumorigenic potential of the cell. The long term goal of this research proposal is to further our understanding of the function of mutant p53 in promoting malignant transformation. Little is known about the "gain of fiinction" expressed by mutant p53 in promoting tumorigenicity. The gain of fiinction phenotype of mutant p53 is supported by the finding that the expression of exogenous mutant p53 in a cell line that is non-tumorigenic and devoid of endogenous p53 protein can transform these cells into a tumorigenic cell line. In addition, mutant p53 protein must be nuclear localized to enhance the tumorigenlc potential of the ceU, suggesting that mutant p53 may fiinction as a regulator of gene expression. Consistent with this hypothesis, mutant human p53 alleles, unlike the wild-type p53 protein, can selectively transactivate the human multi-drug resistance promoter in transient transfection assays using cells that are devoid of endogenous p53 protein. To advance our understanding of the mutant p53-gain-of-fiinction phenotype, we specifically propose to detail the molecular mechanisms by which mutant p53 fiinctions as a transactivator of gene expression by addressing the following questions: 1) What DNA sequences of the MDR promoter are required for mutant p53 trans tivation? 2) Is the endogenous MDR gene transactivated by mutant p53 in stably transfected cells? 3) What domains of mutant p53 are required for transactivation? 4) Does mdm-2, a p53 associated protein, mediate or regulate mutant p53 transactivation function? The proposed research will contribute to our general understanding of how mutant p53 may fiinction in cooperation with other factors, such as mdm-2, to promote tumorigenicity.