The RNA-binding protein KSRP promotes decay of beta-catenin mRNA and is inactivated by PI3K-AKT signaling.

• Main Authors: Roberto Gherzi, Michele Trabucchi, Marco Ponassi, Tina Ruggiero, Giorgio Corte, Christoph Moroni, Ching-Yi Chen, Khalid S Khabar, Jens S Andersen, Paola Briata
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2006-12-01
• Series: PLoS Biology
• Online Access: https://doi.org/10.1371/journal.pbio.0050005
• ISSN: 1544-9173; 1545-7885

Beta-catenin plays an essential role in several biological events including cell fate determination, cell proliferation, and transformation. Here we report that beta-catenin is encoded by a labile transcript whose half-life is prolonged by Wnt and phosphatidylinositol 3-kinase-AKT signaling. AKT phosphorylates the mRNA decay-promoting factor KSRP at a unique serine residue, induces its association with the multifunctional protein 14-3-3, and prevents KSRP interaction with the exoribonucleolytic complex exosome. This impairs KSRP's ability to promote rapid mRNA decay. Our results uncover an unanticipated level of control of beta-catenin expression pointing to KSRP as a required factor to ensure rapid degradation of beta-catenin in unstimulated cells. We propose KSRP phosphorylation as a link between phosphatidylinositol 3-kinase-AKT signaling and beta-catenin accumulation.