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Nature Cell Biology 4, 337–342 (1 May 2002) | doi:10.1038/ncb782

Par-1 regulates stability of the posterior determinant Oskar by phosphorylation

Veit Riechmann , Gustavo J. Gutierrez , Paolo Filardo , Angel R. Nebreda & Anne Ephrussi

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.