Mechanism of regulation of the hypoxia-inducible factor-1 alpha by the von Hippel-Lindau tumor suppressor protein.
In normoxic cells the hypoxia-inducible factor-1 alpha (HIF-1 alpha) is rapidly degraded by the ubiquitin-proteasome pathway, and activation of HIF-1 alpha to a functional form requires protein stabilization. Here we show that the product of the von Hippel-Lindau (VHL) tumor suppressor gene mediated ubiquitylation and proteasomal degradation of HIF-1 alpha under normoxic conditions via interaction with the core of the oxygen-dependent degradation domain of HIF-1 alpha. The region of VHL mediating interaction with HIF-1 alpha overlapped with a putative macromolecular binding site observed within the crystal structure of VHL. This motif of VHL also represents a mutational hotspot in tumors, and one of these mutations impaired interaction with HIF-1 alpha and subsequent degradation. Interestingly, the VHL binding site within HIF-1 alpha overlapped with one of the minimal transactivation domains. Protection of HIF-1 alpha against degradation by VHL was a multistep mechanism, including hypoxia-induced nuclear translocation of HIF-1 alpha and an intranuclear hypoxia-dependent signal. VHL was not released from HIF-1 alpha during this process. Finally, stabilization of HIF-1 alpha protein levels per se did not totally bypass the need of the hypoxic signal for generating the transactivation response.
Pubmed ID: 10944113 RIS Download
Amino Acid Sequence | Animals | Binding Sites | COS Cells | Cell Line | Crystallography, X-Ray | Cysteine Endopeptidases | DNA-Binding Proteins | Fungal Proteins | Green Fluorescent Proteins | Humans | Hypoxia | Hypoxia-Inducible Factor 1 | Hypoxia-Inducible Factor 1, alpha Subunit | Immunoblotting | Ligases | Luminescent Proteins | Models, Biological | Molecular Sequence Data | Multienzyme Complexes | Mutation | Nuclear Proteins | Oxygen | Plasmids | Precipitin Tests | Proteasome Endopeptidase Complex | Protein Structure, Tertiary | Proteins | Saccharomyces cerevisiae Proteins | Sequence Homology, Amino Acid | Signal Transduction | Transcription Factors | Transcriptional Activation | Transfection | Tumor Suppressor Proteins | Ubiquitin-Protein Ligases | Ubiquitins | Von Hippel-Lindau Tumor Suppressor Protein