CONTROL OF MEMBRANE BINDING AND ONCOGENES BY P21RAS

膜结合似乎是转化的关键步骤 Ras蛋白；突变的ras蛋白是胞质的，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。肥胖者的依恋 酸性棕榈酸酯是第一个被鉴定的C-末端修饰， 推测这是RAS与膜相关的主要原因。三 最近发现了更多的处理步骤--移除 最后的3C末端残基，新暴露的α-甲基化- 羧基，以及相当不寻常的异戊二烯基团的附着。 这些修饰，特别是添加了C15(法尼基) 碳氢化合物，有可能参与膜缔合 拉斯。要发现RAS的这些新修饰，就必须重新进行 对我们关于老鼠如何结合到膜上的想法进行评估。这 应用程序建议检查羧基末端修饰， 强调法尼化，以确定每一步对 膜结合。目标是了解RAS如何与 膜，目的是开发破坏这种相互作用的方法，如 抑制转化的新方法，而不是通过控制酶 活性，但通过空间调节ras对蛋白质的访问 触发或传递其致癌信号。 法尼化在膜结合和转化中的作用 将通过两种方式进行检测：通过构建编码 其中修饰在途径的每一步都被中断的蛋白质； 并通过检测法尼化的ras转化细胞的生长情况 已经被禁止了。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.