AFP GENE EXPRESSION AND CARCINOGENESIS

编码血清蛋白甲胎蛋白（AFP）的大鼠基因是 在胎儿肝脏和卵黄囊中活跃，但出生后被抑制。 在成人中，AFP基因可以在一定的条件下重新表达。 异常情况，如在肝癌发生过程中和 部分肝切除的再生 AFP基因也是 在某些可移植性肝细胞癌中有活性 （肝细胞瘤），以及来源于这些的细胞系。 表达 AFP基因的表达是一个很好的模型系统， 基因的发育调控，以及这种调控如何成为 在癌症中改变。 解决这个问题的遗传学方法是 因为肝癌细胞系可以用 突变和重排的AFP基因。 此外，可移植 肝癌、正常肝和癌前肝可提供大的 大量的材料用于隔离可能 参与AFP基因调控。 这种强大的组合， 将利用各种方法来回答关于以下方面的具体问题： 大鼠AFP基因在这些病理状态下是如何调节的。 以前的工作（由其他人）已经定义了三个DNA序列 AFP基因的5'端元件参与组织特异性 表达：（1）5'端-7和-4 kb之间的增强子 在细胞中增加AFP基因的表达， 产生AFP;（2）在约- 3.5在AFP阳性细胞中降低AFP基因表达的kb 系;和（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， 进一步定义这些元素的结构，并回答 关于这些元素如何共同发挥作用来调节 基因转录 其他研究将确定DNA酶I是否 超敏位点对于AFP基因转录是重要的， 是否重复DNA序列映射在5'剥落 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。 这些研究将导致 直接用于纯化特定的核蛋白， AFP调节元件，并分离单克隆抗体 针对这些核蛋白的抗体。 这项工作将 最终可以完全理解基因是如何 表达在癌变过程中和肿瘤组织中发生改变， 状态

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.