TRANSLATION INITIATION IN MULTICELLULAR EUKARYOTES

翻译起始因子eIF-2α的磷酸化已被证明是控制真核细胞蛋白质合成的主要机制，然而这一调控在整个生物体中的发育和生理后果在很大程度上是未知的。通过使用果蝇遗传学的各种工具，我们建议关键地测试eIF-2α磷酸化的功能重要性，并另外研究eIF-2α激酶GCN2的功能。在低等真核生物中，GCN2感受氨基酸缺失，并通过一般调控途径下调氨基酸生物合成基因的表达。在高等真核生物中，GCN2的功能尚不清楚，但由于其在发育和成熟的中枢神经系统中的表达，以及高等真核生物对氨基酸缺失的反应取决于必需氨基酸或非必需氨基酸是限制性的，因此GCN2的功能可能更加复杂。这一建议最重要的目标是分离eIF-2α和GCN2功能突变的缺失。功能突变的丧失可能会给我们提供关于发育功能的即时线索，这些突变将形成其他几个特定目标的基础。还建议进行其他实验，以确定GCN2的下游靶点，以及由eIF-2α磷酸化介导的翻译启动控制所影响的特定发育和生理过程。

Phosphorylation of the translation initiation factor eIF-2alpha has been shown to be a major mechanism controlling protein synthesis in eukaryotic cells, yet the developmental and physiological consequences of this regulation are largely unknown in whole organisms. By using the diverse tools of Drosophila genetics we propose to critically test the functional importance of eIF-2alpha phosphorylation and, in addition, investigate the function of an eIF-2alpha kinase, GCN2. In lower eukaryotes, GCN2 senses amino acid deprivation and through the general control pathway derepresses amino acid biosynthesic genes. In higher eukaryotes the function of GCN2 is unknown but likely to be more complex by virtue of its expression in the developing and mature central nervous system and because the response to amino acid deprivation in higher eukaryotes is dependent upon whether essential or non- essential amino acids are limiting. The most important objective of this proposal is the isolation of loss of function mutations of eIF-2alpha and GCN2. Loss of function mutations are likely to give us immediate clues as to developmental functions and these mutations will be form the basis of several of the other specific aims. Other experiments are proposed to identify downstream targets of GCN2 and specific developmental and physiological processes impacted by the control of translation initiation as mediated by the phosphorylation of eIF-2alpha.