Degradation of the transcription factor Twist, an oncoprotein that promotes cancer metastasis.

Basic helix-loop-helix (bHLH) transcription factor Twist is one of the key inducers of epithelial to mesenchymal transition (EMT) that is a transdifferentiation program associated with embryo development and tumor metastasis. High level of Twist expression is shown to be correlated with cancer malignancy. Although Twist has been reported to be degraded by F-box and leucine-rich repeat protein 14 (FBXL14), the molecular mechanisms by which Twist levels are regulated have not been fully elucidated. In the present study, we identified Twist to be a ubiquitin substrate of β-transducin repeat-containing protein (β-TRCP), the adaptor subunit of SCF(β-TRCP) (Skp1-Cul1-F-box protein) E3 ligase complex. We observed that depletion of β-TRCP leads to an accumulation of Twist protein, which could enhance tumor cell motility and cancer metastasis. Moreover, phosphorylation of Twist by inhibitor of KappaB kinase β (IKKβ) at multiple sites triggers its cytoplasmic translocation and the destruction by SCF(β-TRCP). Thus, our results provide the potential molecular mechanism of how the mesenchymal marker Twist is degraded, thereby shedding lights into regulation of the EMT, and providing the rationale for development of new therapeutic intervention to achieve better treatment outcomes in human cancer.