EMBL Guest Seminar

	Title:	Assembly of an RNP Complex for Intracellular mRNA Transport and Translational Control
	Speaker:	Dr. Anne Ephrussi Unit Coordinator, Developmental Biology Unit, EMBL Heidelberg, Germany
	Place:	National Institute for Basic Biology Meeting room (111)
	Date:	April 12 (Wed), 2006
	Abstract:	The coupling of mRNA localization to translational control is a conserved strategy that allows precise spatial and temporal control of protein expression within cells [1]. The Drosophila oocyte is an ideal model for studying the mechanism of RNA localization-dependent translational control [2]. oskar mRNA, which encodes the posterior determinant of the fly, is localized to the posterior of the oocyte during oogenesis and is translationally repressed prior to localization at the posterior pole. Assembly of a functional oskar mRNA localization complex begins in the nucleus with the splicing-dependent deposition Exon Junction Complex proteins at the first exon-exon junction in the mRNA [3]. The oskar 3’UTR is necessary (but not sufficient) for mRNA localization to the posterior pole, and mediates co-assembly of oskar mRNA into transport complexes. oskar translational repression, which is coupled to mRNA transport, is mediated by Bruno protein. It has been shown that Bruno repressor binds to specific sequences in the oskar 3’UTR and to Cup, an eIF4E-binding protein with which Bruno interacts, suggesting a model for oskar translational repression at initiation [4]. In vitro analysis has recently revealed that, in addition to the proposed mechanism, a second, novel repression mechanism cooperates to ensure tight control of oskar mRNA translation [5]. The molecular mechanisms underlying oskar mRNP complex assembly, localization and translational control will be discussed. 1. St Johnston, D., Nat Rev Mol Cell Biol, 2005. 6(5): p. 363-75. 2. Riechmann, V. and A. Ephrussi, Curr Opin Genet Dev, 2001. 11(4): p. 374-83. 3. Hachet, O. and A. Ephrussi, Nature, 2004. 428(6986): p. 959-63. 4. Nakamura, A., K. Sato, and K. Hanyu-Nakamura, Dev Cell, 2004. 6(1): p. 69-78. 5. Chekulaeva, M., M.W. Hentze, and A. Ephrussi, Cell, 2006. 124(3): p. 521-33.