HIF-1alpha, one of the most extensively studied oncogenes, is activated by a variety of microenvironmental factors. The resulting biological effects are thought to depend on its transcriptional activity. The RNAse enzyme Dicer is frequently downregulated in human cancers, which has been functionally linked to enhanced metastatic properties; however, current knowledge of the upstream mechanisms regulating Dicer is limited. In the present study, we identified Dicer as a HIF-1alpha-interacting protein in multiple types of cancer cell lines and different human tumors. HIF-1alpha downregulated Dicer expression by facilitating its ubiquitination by the E3 ligase Parkin, thereby enhancing autophagy-mediated degradation of Dicer, which further suppressed the maturation of known tumor suppressors, such as the microRNA let-7 and microRNA-200b. Consequently, expression of HIF-1alpha facilitated epithelial-mesenchymal transition (EMT) and metastasis in tumor-bearing mice. Thus, this study uncovered a connection between oncogenic HIF-1alpha and the tumor-suppressive Dicer. This function of HIF-1alpha is transcription independent and occurs through previously unrecognized protein interaction-mediated ubiquitination and autophagic proteolysis.
Date:
2018-02
Relation:
Journal of Clinical Investigation. 2018 Feb;128(1):625-643.
