Hypoxia-induced SUMOylation of E3 ligase HAF determines specific activation of HIF2 in clear-cell renal cell carcinoma.

Clear-cell renal cell cancer (CRCC) is initiated typically by loss of the tumor-suppressor VHL, driving constitutive activation of hypoxia-inducible factor-1 (HIF1) and HIF2. However, whereas HIF1 has a tumor-suppressor role, HIF2 plays a distinct role in driving CRCC. In this study, we show that the HIF1α E3 ligase hypoxia-associated factor (HAF) complexes with HIF2α at DNA to promote HIF2-dependent transcription through a mechanism relying upon HAF SUMOylation. HAF SUMOylation was induced by hypoxia, whereas HAF-mediated HIF1α degradation was SUMOylation independent. HAF overexpression in mice increased CRCC growth and metastasis. Clinically, HAF overexpression was associated with poor prognosis. Taken together, our results show that HAF is a specific mediator of HIF2 activation that is critical for CRCC development and morbidity. ©2014 American Association for Cancer Research.