Nuclear-Cytoplasmic Shuttling of Menin Regulates Nuclear Translocation of β-Catenin

Abstract

ABSTRACT Menin, which is encoded by the multiple endocrine neoplasia type 1 (MEN1) gene, is a tumor suppressor and transcriptional regulator. Menin controls proliferation and apoptosis of cells, especially pancreatic β cells. We have found that menin contains two functional nuclear export signals and that there is nuclear accumulation of β-catenin in Men1 -null mouse embryonic fibroblasts and insulinoma tissues from β-cell-specific Men1 knockout mice. It is reported that the deregulation of Wnt/β-catenin signaling caused by inactivation of tumor suppressors results in abnormal development or tumorigenesis. We further revealed that overexpression of menin reduces β-catenin nuclear accumulation and its transcriptional activity. Menin is able to directly interact with β-catenin and carry β-catenin out of the nucleus via nuclear-cytoplasmic shuttling in a CRM1-dependent manner. These results imply that menin may control cell proliferation through suppression of Wnt/β-catenin signaling.