Hsp70 and CHIP selectively mediate ubiquitination and degradation of hypoxia-inducible factor (HIF)-1alpha but Not HIF-2alpha.
Hypoxia-inducible factors (HIFs) are transcription factors that mediate adaptive responses to reduced oxygen availability. HIF-alpha subunits are stabilized under conditions of acute hypoxia. However, prolonged hypoxia leads to decay of HIF-1alpha but not HIF-2alpha protein levels by unknown mechanisms. Here, we identify Hsp70 and CHIP (carboxyl terminus of Hsc70-interacting protein) as HIF-1alpha-interacting proteins. Hsp70, through recruiting the ubiquitin ligase CHIP, promotes the ubiquitination and proteasomal degradation of HIF-1alpha but not HIF-2alpha, thereby inhibiting HIF-1-dependent gene expression. Disruption of Hsp70-CHIP interaction blocks HIF-1alpha degradation mediated by Hsp70 and CHIP. Inhibition of Hsp70 or CHIP synthesis by RNA interference increases protein levels of HIF-1alpha but not HIF-2alpha and attenuates the decay of HIF-1alpha levels during prolonged hypoxia. Thus, Hsp70- and CHIP-dependent ubiquitination represents a molecular mechanism by which prolonged hypoxia selectively reduces the levels of HIF-1alpha but not HIF-2alpha protein.
Pubmed ID: 19940151 RIS Download
Basic Helix-Loop-Helix Transcription Factors | Cell Hypoxia | Cell Line | Cell Line, Tumor | HSP70 Heat-Shock Proteins | Humans | Hypoxia-Inducible Factor 1, alpha Subunit | Immunoblotting | Immunoprecipitation | Mutation | Proteasome Endopeptidase Complex | Protein Binding | RNA Interference | Transfection | Ubiquitin-Protein Ligases | Ubiquitination