Homotypic association between tumour-associated VHL proteins leads to the restoration of HIF pathway.

The von Hippel-Lindau (VHL) tumour suppressor gene encodes a substrate-specifying component of an E3 ubiquitin ligase that targets hypoxia-inducible factor (HIF) alpha subunits for degradation under normoxia. The VHL protein is composed of an N-terminal HIFalpha-binding beta domain and a C-terminal alpha domain, which is necessary and sufficient for the ...
formation of the E3 multiprotein enzyme. A large number of disease-causing mutations in either the alpha or beta domain renders HIFalpha stable irrespective of oxygen tension, leading to the upregulation of numerous HIF-target genes, such as GLUT1 and VEGF. Here, we show that VHL forms a self-associated complex in vivo, but not in vitro, and demonstrate that coexpression of two different VHL missense mutants -- one in the alpha domain and the other in the beta domain -- restores HIF-mediated gene expression profile. These findings indicate that VHL homotypic complexes can function in vivo in a complementary fashion to target HIFalpha for ubiquitin-mediated proteolysis, and potentially explain why VHL-associated tumours with a missense mutation-carrying VHL allele is almost invariably accompanied by a second VHL allele harbouring a gross truncation or deletion.
Mesh Terms:
Amino Acid Substitution, Bone Neoplasms, Carcinoma, Renal Cell, Cell Line, Tumor, Dimerization, Humans, Hypoxia-Inducible Factor 1, alpha Subunit, Kidney Neoplasms, Mutation, Missense, Neoplasm Proteins, Osteosarcoma, Oxygen, Protein Interaction Mapping, Protein Structure, Tertiary, Structure-Activity Relationship, Transcription Factors, Transfection, Ubiquitin-Protein Ligase Complexes, Ubiquitin-Protein Ligases, Up-Regulation, Von Hippel-Lindau Tumor Suppressor Protein
Oncogene
Date: May. 18, 2006
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