AFP GENE EXPRESSION AND CARCINOGENESIS

编码血清甲胎蛋白(AFP)的大鼠基因是 活跃于胎肝和卵黄囊，但在出生后被抑制。 在成人体内，甲胎蛋白基因在一定条件下可以重新表达。 异常情况，如在肝癌发生过程中和在 肝部分切除术后的再生。甲胎蛋白基因也是 在一些可移植的肝细胞癌中很活跃 (肝癌)，以及从这些细胞系衍生的细胞系。表达方式 甲胎蛋白基因的克隆是一种很好的模型系统 基因的发育调控，以及这种调控是如何形成的 在癌症中发生了变化。解决这个问题的一种遗传方法是 这是因为肝癌细胞系可以被 甲胎蛋白基因突变和重排。此外，可移植 肝癌、正常肝脏和癌前病变肝脏可提供大量 用于分离因素的数量可能是 参与甲胎蛋白基因调控。这一强大的组合 将利用各种方法回答有关以下方面的具体问题 大鼠甲胎蛋白基因在这些病理状态下是如何调控的。 以前的工作(由其他人)定义了三个DNA序列 甲胎蛋白基因中与组织特异性有关的5‘元件 表达：(1)和5‘端-7到-4kb之间的增强子 这增加了AFP基因在细胞中的表达 产生甲胎蛋白；(2)负调控元件(NRE)约- 3.5kb降低甲胎蛋白阳性细胞中甲胎蛋白基因表达 以及(3)仅在AFP中起作用的组织特异性启动子 阳性细胞系。将进行基因转移实验，以 进一步定义这些要素的结构并回答 关于各要素如何共同发挥调节作用的问题 基因转录。其他研究将确定DNase I是否 超敏部位对甲胎蛋白基因转录和转录具有重要作用 重复DNA序列在5‘端剥落中的映射 区域均与AFP基因表达有关。生化 研究将确定与核蛋白结合的DNA序列 并将这些DNA序列与 那些在基因实验中定义的基因。这些研究将导致 直接用于纯化结合的特定核蛋白 AFP调控元件，并对其进行了单抗的分离 这些核蛋白的抗体。这项工作将 最终导致对基因是如何 在癌变过程中和在肿瘤中的表达发生变化 州政府。

The rat gene encoding the serum protein alphafetoprotein (AFP) is active in the fetal liver and yolk sac, but is repressed after birth. In the adult, the AFP gene can be re-expressed under certain abnormal conditions, such as during hepatocarcinogenesis and in regeneration of a partial hepatectomy. The AFP gene is also active in some transplantable hepatocellular carcinomas (hepatomas), and in cell lines derived from these. The expression of the AFP gene makes an excellent model system for the development regulation of genes, and how this regulation becomes changed in cancer. A genetic approach to this problem is available because hepatoma cell lines can be transfected with mutated and rearranged AFP genes. In addition, transplantable hepatomas, normal liver and premalignant liver can provide large amounts of material for the isolation of factors that might be involved in AFP gene regulation. This powerful combination of approaches will be exploited to answer specific questions about how the rat AFP gene is regulated in these pathological states. Previous work (by others) has defined three DNA sequence elements 5' of the AFP gene that are involved in tissue specific expression: (1) and enhancer between -7 and -4 kb of the 5' end that increases the expression of the AFP gene in cells that produce AFP; (2) a negative regulatory element (NRE) at about - 3.5 kb that reduces AFP gene expression in AFP positive cell lines; and (3) a tissue specific promoter that functions only in AFP positive cell lines. Genes transfer experiments will be done to further define the structures of these elements and to answer questions about how the elements function together to regulate gene transcription. Other studies will determine whether DNase I hypersensitive sites are important for AFP gene transcription and whether repetitive DNA sequences mapping in the 5' flaking region are involved with AFP gene expression. Biochemical studies will identify DNA sequences that bind nuclear proteins from liver and hepatomas and to relate these DNA sequences to those defined in genetic experiments. These studies will lead directly to the purification of specific nuclear proteins that bind AFP regulatory elements, and to the isolation of monoclonal antibodies against these nuclear proteins. This work will ultimately lead to a complete understanding of how gene expression is altered during carcinogenesis and in the neoplastic state.