CONTROL OF MEMBRANE BINDING AND ONCOGENES BY P21RAS

膜结合似乎是转化的重要步骤， ras蛋白;胞质中的突变ras蛋白不能引起 转型 Ras经历了一系列的羧基末端修饰 产生膜结合形式的蛋白质。 脂肪的附着 酸棕榈酸酯是第一个确定的C-末端修饰， 推测这可能是ras与膜结合的主要原因。 三 最近已经发现了另外的处理步骤--除去 最后3个C-末端残基，新暴露的α-甲基化， 羧基，和类异戊二烯部分的相当不寻常的连接。 这些修饰，特别是添加C15（法呢基） 碳氢化合物，有可能参与膜缔合， 拉斯 这些新的ras修饰的发现需要重新- 来评估我们关于老鼠如何与细胞膜结合的想法。 这 本申请提出用一种新的方法来检查羧基末端修饰， 强调法尼基化，以确定每个步骤对 膜结合 目的是了解ras如何与 膜，目的是开发破坏这种相互作用的方法， 抑制转化的新方法，而不是通过控制酶 活性，而是通过空间调节ras与蛋白质的接触， 触发或传递致癌信号。 法尼基化对膜结合和转化的贡献 将从两个方面进行研究：通过构建突变ras基因编码 其中修饰在途径的每个步骤被中断的蛋白质; 并通过检查其中法尼基化 被抑制了 这些研究应该提供一个更清晰的理解 膜结合如何控制ras转化活性。

Membrane association appears to be an essential step for transformation by ras proteins; mutated ras proteins which are cytosolic fail to cause transformation. Ras undergoes a series of carboxy terminal modifications which generate the membrane-bound form of protein. Attachment of the fatty acid palmitate was the first C-terminal modification identified, and was presumed to be the major reason that ras associated with membranes. Three additional processing steps have been discovered very recently--removal of the final 3 C-terminal residues, methylation of the newly exposed alpha- carboxyl group, and the quite unusual attachment of an isoprenoid moiety. These modifications, particularly the addition of the C15 (farnesyl) hydrocarbon, have the potential to participate in membrane association of ras. The discovery of these new modifications of ras necessitates a re- evaluation of our ideas about how rats binds to membranes. This application proposes to examine carboxy terminal modifications, with an emphasis on farnesylation, to determine each steps' contribution to membrane binding. The goal is to understand how ras interacts with membranes with the aim of developing means to disrupt this interaction as novel methods to inhibit transformation, not by controlling enzymatic activity, but by spatially regulating access of ras to proteins which trigger or transmit its oncogenic signal. The contribution of farnesylation to membrane binding and transformation will be examined in two ways: by constructing mutant ras genes encoding proteins in which modification is interrupted at each step of the pathway; and by examining the growth of ras-transformed cells in which farnesylation has been inhibited. These studies should provide a clearer understanding of how membrane binding controls ras transforming activity.