Identifying Novel Intensity-Specific Regulators of RAS Signaling

摘要 哺乳动物的RAS小GTP酶家族，由HRAS、NRAS和KRAS组成，突变后保留在 在五分之一的人类癌症中处于活跃的致癌状态。通常情况下，这些突变发生得较早， 肿瘤发生学。在三个家族成员中，KRAS突变最频繁，这表明这一基因的某些特征 基因使其更有可能启动肿瘤的发生。为此，我们小组将高频与 KRAS突变为稀有密码子的偏向，导致编码的mRNA翻译不良。从机械上讲， 较低水平的KRAS蛋白和KRAS/MAPK信号强度绕过了生长停滞反应 衰老，从而允许诱导肿瘤的启动。相反，KRAS mRNA的翻译不佳是 在疾病后期克服，促进肿瘤进展。因此，不同水平的KRAS/MAPK信号 强度决定了癌症起始和进展过程中不同的表型输出。因此，必须有 控制RAS信号强度的不同因素，这些因素在任何一种肿瘤中都应该是关键的 开始或肿瘤进展。这样的监管机构具有很大的临床相关性，并可能为 一类全新的RAS信号调控器用于治疗干预。我的长期目标是确定 并在治疗上针对“RAS强度特异性调节器”。为了确定这些监管者，我们小组采取了 果蝇粗眼表型对不同水平RAS异常敏感的优势 发信号。我们采用了改变果蝇RAS基因密码子用法的新方法来比较 高RAS和低RAS信号。然后，我们利用这两种遗传背景在体内进行了第一次 强度特定调节器筛选，并确定了15个不足之处。一个缺陷被映射到 核糖体蛋白S21(Rps21)基因，它是RAS信号的抑制因子。因此，我计划调查 Rps21抑制RAS信号的基本机制(目标1)。此外，我的目标是确定其他 RAS信号在剩余缺陷中的新强度特异性调节因子及其在RAS中的作用 哺乳动物环境中的肿瘤发生(目标2)。完成这些目标将建立新的联系 在翻译控制和RAS信号之间，揭示了RAS驱动的癌症中新的遗传脆弱性，以及 最终可以挖掘出一系列潜在的治疗靶点，以探索癌症治疗方法。

Abstract The mammalian family of RAS small GTPases, composed of HRAS, NRAS, and KRAS, is mutated to remain in an active, oncogenic state in one fifth of all human cancers. Typically, these mutations occur early, initiating tumorigenesis. Of the three family members, KRAS is mutated most often, suggesting that some feature of this gene renders it more likely to initiate tumorigenesis. To this end, our group linked the high frequency with which KRAS is mutated to a bias of rare codons and resulting poor translation of the encoded mRNA. Mechanistically, the lower levels of KRAS protein and KRAS/MAPK signaling intensity circumvent the growth arrest response of senescence, thereby allowing the induction of tumor initiation. Conversely, poor translation of KRAS mRNA is overcome in later disease stages, promoting tumor progression. Thus, different levels of KRAS/MAPK signaling intensity dictate distinct phenotypic outputs during cancer initiation and progression. Therefore, there must be factors that differentially control Ras signaling intensity, and these factors should be critical during either tumor initiation or tumor progression. Such regulators are of great clinical relevance and could open up the door to a whole new class of regulators of Ras signaling for therapeutic intervention. My long-term goal is to identify and therapeutically target “RAS intensity-specific regulators”. To identify these regulators, our group took advantage of the incredible sensitivity of the Drosophila rough eye phenotype to differential levels of Ras signaling. We employed the novel approach of altering codon usage in the Ras gene of Drosophila to compare high and low Ras signaling. We then exploited these two genetic backgrounds to execute the first-ever in vivo intensity-specific regulator screen and identified fifteen deficiencies. One deficiency was mapped to the Ribosomal protein S21 (Rps21) gene, which acts as a suppressor of Ras signaling. I therefore plan to investigate the underlying mechanism by which Rps21 suppresses Ras signaling (Aim 1). In addition, I aim to identify other novel intensity-specific regulators of Ras signaling in the remaining deficiencies and elucidate their roles in Ras tumorigenesis in the mammalian setting (Aim 2). Completion of these aims will establish new connections between translational control and Ras signaling, reveal new genetic vulnerabilities in RAS-driven cancer, and finally could unearth a pipeline of potential therapeutic targets to explore for cancer therapies.