9305407 Hille Gene expression is regulated by translational control in oocytes and eggs. Immature oocytes store inactive mRNAs, translational initiation factors, and ribosomes, to be used during maturation of the oocyte and during the early cleavage stages of embryogenesis. On hormonal stimulation, immature oocytes undergo meiosis, translational rates increase, and the translational specificity switches from mRNAs that support growth to those that undergo rapid cell divisions. In many animals, including mammals, frogs, and starfish, meiosis and fertilization are coordinated with fertilization occurring in meiosis II, after the first polar body is extruded. Dr. Hille's previous research focused on elucidating mechanisms that activate the translational apparatus during maturation. She has shown that initiation factor eIF-4E is phosphorylated 20 minutes after addition of the maturation hormone to starfish oocytes, at the same time that the translation rate increases. She now proposes to clone starfish eIF-4E so she can determine the amino acid site that is phosphorylated. With the cloned substrate in hand, she will move backward in the cascade of meiotic events, searching for kinases that phosphorylate this initiation factor. This search will have two prongs: purifying starfish cytoplasm in collaboration with Dr. Steven Pelech and testing for eIF-4E kinase activity, and trying to screen expression libraries for a kinase that phosphorylates the starfish eIF-4E. The cloning of the starfish eIF-4E kinase is of general interest since the kinase responsible for phosphorylation of eIF-4E in vivo is not known for any organism. This proposal is a prototype of a signal transduction pathway that initiates growth and development of cells and will increase our basic understanding of how translation is activated through eIF-4E after environmental stimulation, and our general understanding of hormone activation of animal oocytes. ***
