REGULATION OF TRANSFORMING GROWTH FACTORS

转化生长因子-α(TGF-α)是一种多肽有丝分裂原 起源于上皮和间充质的细胞，涉及多种不同的 生物过程包括伤口愈合、细胞迁移、血管生成 和骨吸收。作为EGF生长调节剂家族的一员，它 与EGF受体高亲和力结合并激活其固有的 酪氨酸激酶。其确切的生理功能尚不清楚，但 转化生长因子α在发育中的胚胎和各种成人组织中都有表达。 包括皮肤、脑下垂体腺、蜕膜和大脑，以及激活的 巨噬细胞。然而，转化生长因子α表达的标志是 始终如一的观察表明，它在肿瘤中最为普遍和丰富 细胞。因此，与正常对照组相比，转化生长因子水平 α-mRNA和蛋白在肿瘤和转化的细胞中升高 化学物质、病毒和激活的细胞癌基因。这些数据表明 转化生长因子α参与了肿瘤疾病的发展， 事实上，转化生长因子α可以促进细胞在培养中的转化。 此外，当它在转基因小鼠中表达时，它就像癌蛋白一样 在乳腺和肝脏。因此，转化生长因子α的表达增加 似乎是肿瘤发生中的一个重要事件，通过 它被上调了哪一个是未知的。这样做的长期目标是 建议确定分泌的转化生长因子α和转化生长因子的生理作用 它的整膜前体(proTGFα)，并阐明了 正常组织和肿瘤组织中转化生长因子α表达的调控机制 细胞。我们的具体目标是：(1)确立转化生长因子的职能作用 通过开发转化生长因子α基因在其中 过度表达或全局停用。进一步描述线条的特征 过度表达转化生长因子α的转基因小鼠是一种全局或组织- 具体的方式。后者是通过同源重组实现的 胚胎干细胞。将正确靶向的ES细胞注射到 胚泡，然后转移给养母。建立 对转化生长因子α等位基因失活的嵌合体动物。繁育 这些用来培育杂合系和纯合系。(2)描述 跨膜型转化生长因子α原的生物学活性 确定它可能积累的细胞类型，并开发出 在全球或特定组织中过度表达该基因的转基因小鼠 举止。利用基因打靶技术培育其表达(但 而不是成熟的、分泌的转化生长因子α)被废除。确定 果蝇同源基因的表达、加工和功能 以苍蝇遗传学为特点。(三)找准机制 调节正常和肿瘤细胞中转化生长因子α基因的表达。 定义构成表达所需的启动子元件，以及 建立在细胞中上调表达的机制 被激活的致癌基因转化的。分析结构性变化， 可能伴随着基因表达的增加，并决定是否 改变信使核糖核酸的稳定性调节转化生长因子α的表达。最后，建立 一种用于研究子宫内膜形成机制的子宫内膜培养系统 雌激素促进了该基因的表达。

Transforming growth factor-alpha (TGF alpha), a polypeptide mitogen for cells of epithelial and mesenchymal origin, has been implicated in diverse biological processes including wound healing, cell migration, angiogenesis and bone resorption. A member of the EGF family of growth regulators, it binds to the EGF receptor with high affinity and activates its intrinsic tyrosine kinase. Its precise physiological functions are not known, but TGF alpha is expressed in developing embryos, and in various adult tissues including skin, pituitary gland, decidua and brain, as well as in activated macrophages. The hallmark of TGF alpha expression, however,is the consistent observation that it is most prevalent and abundant in neoplastic cells. Thus, compared to their normal counterparts, the levels of TGF alpha mRNA and protein are elevated in tumors and in cells transformed by chemicals, viruses and activated cellular oncogenes. These data suggest that TGF alpha participates in the development of neoplastic disease and, indeed, TGF alpha promotes the transformation of cells in culture. Additionally, when expressed in transgenic mice it acts as an oncoprotein in mammary gland and liver. Thus, increased expression of TGF alpha appears to be an important event in tumorigenesis though the mechanism by which it is upregulated is unknown. The long term objectives of this proposal are to determine the physiological roles of secreted TGF alpha and its integral-membrane precursor (proTGF alpha), and elucidate the mechanisms that regulate TGF alpha expression in normal and neoplastic cells. Our specific aims are to: (1) Establish functional roles for TGF alpha by developing mice in which the TGF alpha gene is either overexpressed or globally inactivated. Further characterize lines of transgenic mice that overexpress TGF alpha is either a global or tissue- specific manner. Accomplish the latter via homologous recombination is embryonic stem (ES) cells. Inject correctly targeted ES cells into blastocysts which are then transferred to foster mothers. Establish animals that are chimaeric for inactivation of a TGF alpha allele. Breed these to develop hetero- and homozygous lines. (2) Characterize the biological activities of transmembrane proTGF alpha Derive antibodies to identify cell types in which it might accumulate, and develop lines of transgenic mice that overexpress it globally or in a tissue-specific manner. Use gene targeting to develop mice in which its expression (but not that of the mature, secreted TGF alpha) is abolished. Identify a Drosophila homologue so that its expression, processing and function can be characterized with the aid of fly genetics. (3) Identify mechanisms regulating TGF alpha gene expression in normal and neoplastic cells. Define promoter elements required for constitutive expression, and establish mechanisms by which expression is upregulated in cells transformed by activated oncogenes. Analyze for structural changes that might accompany increased gene expression, and determine the whether changing mRNA stability regulates TGF alpha expression. Finally, establish an endometrial culture system with which to study the mechanism by which estrogen enhances expression of this gene.