Figure 3. Stability is increased, while enzymatic function is maintained, in mutant HIF-2α protein. (A) An immunoprecipitation assay demonstrated lower affinity of mutant HIF-2α protein for binding to VHL and subsequent decreases in ubiquitination and proteasome degradation. (B) A cycloheximide assay confirmed that stabilization of mutant HIF-2α extended the half-life of the mutant protein.