REGULATION OF RAS FUNCTION

ras原癌基因的突变与肿瘤的发生有关。 超过20%的人类癌症。 阐明 调节正常ras活性的生化途径 蛋白以及激活的ras蛋白刺激的途径 对我们理解正常细胞生长以及 Ras诱导肿瘤中生化途径的缺陷调节。 而 正常Ras蛋白调节大多数细胞生长和细胞分裂 ras蛋白还可以诱导某些细胞的终末分化 类型 Ras蛋白在非分裂细胞中高度表达， 个脑袋 有证据表明RAS对于维持 神经元表型。 然而，ras蛋白可能具有额外的 在神经元细胞生物学中的生物学作用。 的理解 对大脑中ras功能的调节是定义更多 这正是ras蛋白在神经元中的生物学作用。 这样做的目的之一 建议是审查最近确定的机制， 脊椎动物RAS特异性核苷酸交换因子调节RAS功能。 我们将采用体外生物化学和分子遗传技术， 解决这个目标。 另一个目的是表征脑特异性NEF （cdc25）。 我们将检测cdc 25的致癌潜力， cdc 25-NEF是如何调节的，使用生物化学技术以及 NIH-3 T3细胞致瘤性测定。 另一个目的是确定新的NEFs 其调节ras和ras相关蛋白。 我们将使用生化手段 纯化已知的NEFs;我们还将采用分子遗传筛选， 发现新的NEFs。 新的NEFs的识别和 了解它们如何调节ras或ras相关基因的功能 蛋白质对于理解ras的复杂性至关重要 信号通路 此外，因为ras与很大一部分 在人类肿瘤中，它是化学治疗剂的潜在靶标。 它 对于理解ras在神经元（和其他非神经元）中的功能至关重要。 增殖组织），然后可以 成功开发。

Mutations in the ras proto-oncogenes have been implicated in the development of greater than 20% of all human cancers. The elucidation of the biochemical pathways which regulate the activity of the normal ras proteins as well as the pathways which the activated ras proteins stimulate is critical to our understanding of normal cell growth as well as of the defective regulation of biochemical pathway in ras-induced tumors. While the normal ras proteins regulate growth and cell division for most cell types, ras protein can also induce terminal differentiation of certain cell types. Ras proteins are highly expressed in the non-dividing cells of the brain. There is evidence suggesting ras is critical for the maintenance of the neuronal phenotype. However, ras proteins could have additional biological role(s) in the biology of the neuronal cell. The understanding of the regulation of ras function in the brain is key to defining more precisely the biological role of ras protein in neurons. One aim of this proposal is to examine the mechanism by which the recently-identified vertebrate ras-specific nucleotide-exchange factors regulate ras function. We will employ in vitro biochemical and molecular genetic techniques to address this aim. Another aim is to characterize the brain-specific NEF (cdc25). We will examine the oncogenic potential of cdc25 and investigate how cdc25-NEF is regulated, using biochemical techniques as well as the NIH-3T3 cell oncogenicity assay. Another aim is to identify novel NEFs which regulate ras and ras-related proteins. We will use biochemical means to purify known NEFs; we will also employ molecular genetic screens to discover novel NEFs. The identification of novel NEFs and the understanding of how they regulate the function of ras or ras-related proteins is all-important to an understanding of the complexity of ras pathway signaling. Further, because ras is implicated in a large percent of human tumors, it is a potential target for chemotherapeutic agents. it is critical to understand the function of ras in neurons (and other non- proliferating tissues) before anti-ras chemotherapeutic agents can be successfully developed.