HIF-1α promotes autophagic proteolysis of Dicer and enhances tumor metastasis
Hui-Huang Lai, … , Hiroshi I. Suzuki, Pai-Sheng Chen
Hui-Huang Lai, … , Hiroshi I. Suzuki, Pai-Sheng Chen
Published December 18, 2017
Citation Information: J Clin Invest. 2018;128(2):625-643. https://doi.org/10.1172/JCI89212.
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Research Article Cell biology

HIF-1α promotes autophagic proteolysis of Dicer and enhances tumor metastasis

Abstract

HIF-1α, 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-1α–interacting protein in multiple types of cancer cell lines and different human tumors. HIF-1α 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-1α facilitated epithelial-mesenchymal transition (EMT) and metastasis in tumor-bearing mice. Thus, this study uncovered a connection between oncogenic HIF-1α and the tumor-suppressive Dicer. This function of HIF-1α is transcription independent and occurs through previously unrecognized protein interaction–mediated ubiquitination and autophagic proteolysis.

Authors

Hui-Huang Lai, Jie-Ning Li, Ming-Yang Wang, Hsin-Yi Huang, Carlo M. Croce, Hui-Lung Sun, Yu-Jhen Lyu, Jui-Wen Kang, Ching-Feng Chiu, Mien-Chie Hung, Hiroshi I. Suzuki, Pai-Sheng Chen

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Figure 6

Identification of functional domains required for HIF-1α–Dicer interaction.

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Identification of functional domains required for HIF-1α–Dicer interacti...
(A) Schematic representation of the Myc-tagged truncated HIF-1α used in this study. The immunoblots presented were derived from replicate samples run on parallel gels. (B) FLAG-Dicer and individual Myc-tagged HIF-1α truncations were coexpressed in HCT116 cells. The immunoprecipitates isolated by anti–Myc-tag antibodies were subjected to Western blot analysis to detect the interaction between truncated Myc–HIF-1α and FLAG-Dicer. (C) Effects of HIF-1α with a truncated ID or C-TAD domain on the downregulation of Dicer. Lysates from HCT116 cells expressing full-length HIF-1α or the ΔID or ΔC-TAD truncations were subjected to Western blot analysis. The immunoblots presented were derived from replicate samples run on parallel gels. (D) Schematic representation of the FLAG-tagged truncated Dicer used in this study. (E) Myc–HIF-1α and individual FLAG-tagged Dicer truncations were coexpressed in HCT116 cells. Immunoprecipitates isolated by anti–FLAG-tag antibodies were subjected to Western blot to determine the interaction between truncated Dicer and Myc–HIF-1α. (F) PAZ domain–deleted Dicer was insensitive to HIF-1α–mediated protein degradation. HCT116 cells were transfected with full-length or PAZ truncation of Dicer, and protein stability was monitored in the presence of CHX at the indicated times to block de novo protein synthesis. Data are presented as mean ± SD, with at least n = 3 per group. **P < 0.01, 2-way ANOVA. The experiments depicted in B and E were performed in the presence of CQ and NH4Cl to block autophagy-lysosomal degradation.