Riechmann, V., Gutierrez, G.J., Filardo, P., Nebreda, A.R., Ephrussi, A. (2002). Par-1 regulates stability of the posterior determinant Oskar by phosphorylation.  Nat. Cell Biol. 4(5): 337--342.

FBrf0149128

Research paper

Par-1 kinase is critical for polarization of the Drosophila melanogaster oocyte and the one-cell Caenorhabditis elegans embryo. Although Par-1 localizes specifically to the posterior pole in both cells, neither its targets nor its function at the posterior pole have been elucidated. Here we show that Drosophila Par-1 phosphorylates the posterior determinant Oskar (Osk) and demonstrate genetically that Par-1 is required for accumulation of Osk protein. We show in cell-free extracts that Osk protein is intrinsically unstable and that it is stabilized after phosphorylation by Par-1. Our data indicate that posteriorly localized Par-1 regulates posterior patterning by stabilizing Osk.