ISOPRENYLATION OF RAS AND OTHER PROTEINS IN YEAST

通过添加法尼基对蛋白质进行的修饰已经被 被证明对RAS等蛋白质的功能至关重要。这 促进RAS的膜结合，这是其所需的 转型活动。这种修饰是由蛋白质催化的 识别C端CAAX基序的法尼基转移酶 法尼化蛋白质。这些研究最终导致了 表现出显著阻断能力的法尼基转移酶抑制剂 人类肿瘤细胞的生长。对影响的表征 然而，这些抑制剂增加了蛋白质 除RAS外，其他都是抑制剂的靶点。此外，一个不断增长的 Rheb、RhoB和RhoE等G蛋白的数量已经被证明是 法尼化。这些观察结果引出了一个问题：到底有多少蛋白质 是法尼化的，它们的生理功能是什么。我们的龙 学期目标就是解决这些问题。最近的测定 酵母基因组的整个序列提供了一个独特的机会 来探讨这些问题。在……的研究中是第一次 法尼化，我们可以得到法尼化蛋白质的全貌。 在真核生物中。通过搜索潜在的法尼化 利用酵母蛋白质数据库，我们鉴定了22种蛋白质 以CAAX主题结束。其中，14种是新鉴定的蛋白质。 或部分特化的蛋白质。我们将采取有针对性的方法 以确定这些蛋白质的特性。首先，我们将重点关注两个G蛋白， Rheb和Rho3.Rheb特别有趣，因为它是人类 相应的基因在多种人类肿瘤细胞中表达上调，并已 最近被证明是法尼化的。我们将开展基因工程 破坏和表达突变蛋白以获得洞察力 这种G蛋白的功能。另一款是Rho3，它扮演一个 在酵母细胞极化生长中的关键作用，显然是通过 它对肌动蛋白细胞骨架和膜融合的作用。我们会 探讨法尼化对Rho3功能的影响。 最后，将进行一项系统的基因破坏研究，以 识别新的法尼化蛋白质，这些蛋白质是必不可少的。我们的研究将 是首次对法尼化蛋白质进行全面表征的尝试 在真核生物中。所获得的结果应该戏剧性地 拓宽了我们对蛋白质法尼化的理解。

Modification of proteins by the addition of a farnesyl groups has been shown to be critical for the function of proteins such as Ras. This facilitates membrane association of Ras which is required for its transforming activity. The modification is catalyzed by protein farnesyltransferase which recognizes the C-terminal CAAX motif of farnesylated proteins. These studies culminated in the development of farnesyltransferase inhibitors which exhibit remarkable ability to block the growth of human tumor cells. Characterization of the effects of these inhibitors, however, has raised the possibility that proteins other than Ras are targets of the inhibitors. In addition, a growing number of G-proteins such as Rheb, RhoB and RhoE have been shown to be farnesylated. These observations lead to a question how many proteins are farnesylated and what their physiological functions are. Our long term objective is to address these questions. Recent determination of the entire sequence of the yeast genome provides a unique opportunity to explore these issues. For the first time in the study of farnesylation, we can obtain a complete picture of farnesylated proteins in an eukaryotic organism. By searching for potentially farnesylated proteins using the yeast protein database, we identified 22 proteins ending with the CAAX motif. Of these, 14 are newly identified proteins or partially characterized proteins. We will take a targeted approach to characterize these proteins. First, we will focus on two G-proteins, Rheb and Rho3. Rheb is of particular interest, since its human counterpart is upregulated in a variety of human tumor cells, and has recently been shown to be farnesylated. We will carry out gene disruption as well as expression of mutant proteins to gain insights into the function of this G-protein. The other is Rho3 which plays a critical role in the polarized growth of yeast cells, apparently through its action on actin cytoskeleton and membrane fusions. We will investigate the significance of farnesylation on the function of Rho3. Finally, a systematic gene disruption study will be carried out to identify new farnesylated proteins which are essential. Our study will be the first full scale attempt to characterize farnesylated proteins in an eukaryotic organism. The results obtained should dramatically widen our understanding of protein farnesylation.