Lachance Pascal E D, Miron Mathieu, Raught Brian, Sonenberg Nahum, Lasko Paul
Department of Biology, McGill University, 1205 Ave. Docteur Penfield, Montréal, Québec, Canada H3A 1B1.
Mol Cell Biol. 2002 Mar;22(6):1656-63. doi: 10.1128/MCB.22.6.1656-1663.2002.
Eukaryotic translation initiation factor 4E (eIF4E) binds to the cap structure at the 5' end of mRNAs and is a critical target for the control of protein synthesis. eIF4E is phosphorylated in many systems in response to extracellular stimuli, but biochemical evidence to date has been equivocal as to the biological significance of this modification. Here we use a genetic approach to this problem. We show that, in Drosophila melanogaster, homozygous eIF4E mutants arrest growth during larval development. In Drosophila eIF4EI, Ser251 corresponds to Ser209 of mammalian eIF4E, which is phosphorylated in response to extracellular signals. We find that, in vivo, eIF4EI Ser251 mutants cannot incorporate labeled phosphate. Furthermore, transgenic Drosophila organisms expressing eIF4E(Ser251Ala) in an eIF4E mutant background have reduced viability. Escapers develop more slowly than control siblings and are smaller. These genetic data provide evidence that eIF4E phosphorylation is biologically significant and is essential for normal growth and development.
真核生物翻译起始因子4E（eIF4E）与mRNA 5'端的帽结构结合，是控制蛋白质合成的关键靶点。在许多系统中，eIF4E会响应细胞外刺激而发生磷酸化，但迄今为止，关于这种修饰的生物学意义，生化证据并不明确。在此，我们采用遗传学方法来解决这个问题。我们发现，在黑腹果蝇中，纯合的eIF4E突变体在幼虫发育期间会停止生长。在果蝇eIF4EI中，Ser251对应于哺乳动物eIF4E的Ser209，后者会响应细胞外信号而发生磷酸化。我们发现，在体内，eIF4EI Ser251突变体无法掺入标记的磷酸盐。此外，在eIF4E突变背景下表达eIF4E(Ser251Ala)的转基因果蝇生物体的活力降低。存活者的发育比对照同胞慢，且体型更小。这些遗传学数据证明，eIF4E磷酸化具有生物学意义，对正常生长和发育至关重要。
