Abstract
Several lines of evidence suggest that accumulation of cytoplasmic beta-catenin transduces an oncogenic signal. We show that beta-catenin is ubiquitinated and degraded by the proteosome and that beta-catenin stability is regulated by a diacylglycerol-independent protein kinase C-like kinase activity, which is required for beta-catenin ubiquitination. We also define a six-amino acid sequence found in both beta-catenin and the NF-kappaB regulatory protein IkappaBalpha, which, upon phosphorylation, targets both proteins for ubiquitination. Mutation of a single serine within the ubiquitination targeting sequence prevents ubiquitination of beta-catenin. Mutations within the ubiquitination targeting sequence of beta-catenin may be oncogenic.
Highlights
Teins Wg and Zw3 (Wnt-1 and glycogen synthase kinase 3 (GSK3), respectively) and regulates dorsal axis formation [2]
We show that certain protein kinase C (PKC) inhibitors cause a dramatic accumulation of cytoplasmic -catenin by inhibiting its ubiquitination
-Catenin Is Degraded by the Ubiquitin-Proteosome Pathway—Proteins that are to be degraded by the ubiquitin/proteosome system are first conjugated to multiple copies of the small protein ubiquitin through isopeptide linkages [17]
Summary
Teins Wg and Zw3 (Wnt-1 and glycogen synthase kinase 3 (GSK3), respectively) and regulates dorsal axis formation [2]. We show that certain protein kinase C (PKC) inhibitors cause a dramatic accumulation of cytoplasmic -catenin by inhibiting its ubiquitination. Cells were lysed in Nonidet P-40, separated by SDS-PAGE, and immunoblotted with an anti--catenin monoclonal antibody.
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