Genetic Screens for Drosophila p70 S6 Kinase Modifiers

哺乳动物p70S6激酶，称为S6K1，是一种丝裂原刺激的丝氨酸/苏氨酸激酶，位于导致翻译和细胞生长控制的信号通路上。目前关于S6K1功能的模型是，激活后，S6K1磷酸化40S核糖体亚基蛋白S6，这导致核糖体选择性地增加一组编码核糖体蛋白和翻译起始因子的mrna的翻译。预计这一系列事件将增加核糖体的生物发生和细胞的翻译能力，从而增加一般蛋白质合成和细胞生长。S6K1的活化是复杂的，与激酶中8个氨基酸的磷酸化有关。导致S6K1活化的信号通路只被部分定义，并且只有一种激酶的身份是已知的，这种激酶磷酸化与激酶活化相关的8种磷酸化氨基酸inS6K1中的一种。果蝇S6激酶同源物dS6K在结构和功能上与哺乳动物S6K1保守。在培养细胞中，dS6K可以被激活或抑制S6K1的药物激活或抑制，这表明调节dS6K和S6K1激活的机制在果蝇和哺乳动物之间是保守的。与S6K1在翻译和生长中的作用类似，果蝇中dS6K的作用似乎是调节细胞大小、细胞生长和细胞增殖。这项提议的总体目标是利用果蝇遗传学的力量来识别dS6K通路的新成分。实现这一目标需要：1。测试编码dS6K信号通路可疑成分的基因突变等位基因是否与突变的dS6K等位基因发生遗传相互作用2。筛选果蝇缺陷种群以鉴定dS6K突变表型的剂量敏感修饰因子3。执行诱变筛选，旨在识别编码dS6K信号通路成分的基因中新诱导的突变。确定dS6K信号通路的组成部分对于增加我们对细胞内信号传导的认识非常重要，也应该影响我们对调节翻译和细胞生长的基本机制的理解。

Stewart 0077618AbstractThe mammalian p70S6 kinase, termed S6K1, is a mitogen-stimulated serine/threonine kinase that lies on a signaling pathway leading to the control of translation and cell growth. The current model for S6K1 function is that upon activation, S6K1 phosphorylated the 40S ribosomal subunit protein S6 and this causes the ribosome to selectively increase the translation of a group of mRNAs that encode ribosomal proteins and translation initiation factors. This series of events would be expected to increase ribosome biogenesis and the translational capacity of the cell and thus allow increased general protein synthesis and cell growth. The activation of S6K1 is complex and is associated with the phosphorylation of eight amino acids in the kinase. The signaling pathways that lead to S6K1 activation are only partially defined and only the identity of one of the kinases that phosphorylates one of the eight phosphorylated amino acids inS6K1 that are associated with the activation of the kinase is known. The Drosophila melanogaster S6 kinase homolog, dS6K, is structurally and functionally conserved with the mammalian S6K1. In cultured cells, dS6K can be activated or inhibited by agents that activate or inhibit S6K1, suggesting that the mechanisms that regulate dS6K and S6K1 activation will be conserved between Drosophila and mammals. Similar to the proposed role for S6K1 in translation and growth, the role for dS6K within the fly appears to be in regulating cell size, cell growth and cell proliferation. The overall goal of this proposal is to use the power of Drosophila genetics to identify novel components of the dS6K pathway. Reaching this goal will entail:1. Testing if mutant alleles of genes that encode suspected components of the dS6K signaling pathway interact genetically with mutant dS6K alleles2. Screening a collection of Drosophila deficiency stocks to identify dose-sensitive modifiers of dS6K mutant phenotypes3. Performing mutagenesis screens designed to identify newly induced mutations in genes that encode components of the dS6K signaling pathways.Identifying components of the dS6K signaling pathways will be important for increasing our knowledge of intracellular signaling and also should impact our understanding of the basic mechanisms that regulate translation and cell growth.