SUMOylation of hypoxia-inducible factor-1α reduces its transcriptional activity

• DOI: 10.1016/j.bbrc.2007.06.103
• Publication Date: 2007-06-28T09:03:25Z
• Authors: Mélanie A. Berta; Nathalie Mazure; Maurice Hattab; Jacques Pouysségur; M. Christiane Bra...
• Keywords: 0301 basic medicine; 0303 health sciences; Transcription, Genetic; Recombinant Fusion Proteins; SUMO-1 Protein; Down-Regulation; Hypoxia-Inducible Factor 1, alpha Subunit; 3. Good health; 03 medical and health sciences; [SDV.CAN] Life Sciences [q-bio]/Cancer; [SDV.BBM] Life Sciences [q-bio]/Biochemistry, Molecular Biology; Mutagenesis, Site-Directed; Small Ubiquitin-Related Modifier Proteins; Humans; RNA, Small Interfering; Glutathione Transferase; HeLa Cells

The hypoxic response of mammalian cells is controlled through a transcriptional pathway that is mediated by the hypoxia-inducible factor (HIF). Here, we show that HIF-1alpha undergoes post-translational modification by the three isoforms of the small ubiquitin-related modifier (SUMO-1, -2 and -3) in vitro in proximity to and within the oxygen-dependent degradation domain (ODDD). SUMO conjugation is promoted in vitro by the E3 SUMO ligase RanBP2/Nup538 and SUMO modification in vivo does not change HIF-1alpha turnover rate. Using cotransfection of siRNA targeted to endogenous HIF-1alpha together with HIF-1alpha siRNA-resistant expression vectors carrying mutations for SUMO modification we demonstrate increased hypoxia-response element-dependent transcriptional activity for SUMO-deficient HIF-1alpha. These results indicate that when HIF-1alpha is conjugated to SUMO its transcriptional activity is decreased and that this is not mediated by a change in the protein's half-life.